E. coli specific antibody sequences

ABSTRACT

The invention refers to an isolated antibody that specifically binds to O25b antigen of  E. coli  strains comprising at least an antibody heavy chain variable region (VH), which comprises any of the CDR1 to CDR3 sequences as listed in FIG.  1 , and optionally further comprising an antibody light chain variable region (VL), which comprises any of the CDR4 to CDR6 sequences as listed in FIG.  1 , or functionally active CDR variants of any of the forgoing CDR 1-6 sequences.

FIELD OF THE INVENTION

The invention refers to an isolated antibody that specifically binds to O25b antigen of E. coli strains and is characterized by specific CDR sequences.

BACKGROUND OF THE INVENTION

Lipopolysaccharide (LPS) is the most abundant antigen on the surface of enterobacterial pathogens. Typically, LPS has three structural parts: i) Lipid A (also known as endotoxin), ii) core oligosaccharide, and iii) O-antigen. The latter is made up of repeating subunits of 3-6 sugars (depending on the serotype). Lipid A and core OS are relatively well conserved in one single enterobacterial species, however, their accessibility to antibodies are limited. On the other hand, O-antigens are highly accessible, but very diverse with respect to their structure (in E. coli there are ˜180 different O-typoc).

Antibodies against O-antigens are able to bind to the surface of E. coli, hence they are used both for diagnostics (e.g. O-typing for epidemiology studies) as well as are proposed as therapeutic measures. Nevertheless, given the huge structural variability, a broad spectrum protection with O-antigen specific antibodies is cumbersome.

Extraintestinal infections caused by E. coli are common causing significant morbidity and mortality. Multi-drug resistant (MDR) strains of E. coli that have emerged recently cause a significant proportion of E. coli infections.

Treatment options against these MDR strains are getting very limited as they have evolved resistance to most classes of clinically relevant antibiotics. Therefore, an alternative treatment option, e.g. passive immunization with monoclonal antibodies (mAbs) holds a great promise for the future.

In the past years a well-defined clonal lineage of MDR E. coli. the ST131-O25b:H4 has emerged causing approximately 10% of all extraintestinal E. coli infections and about half of the MDR E. coli infections (Peirano et al. Int J Antimicrob Agents 2010 April; 35(4):316-21; Rogers et al. J Antimicrob Chemother 2011 January; 66(1):1-14; Woodford et al. FEMS Microbiol Rev 2011 September; 35(5):736-55). Strains belonging to this lineage show limited heterogeneity thus could be considered very similar with respect to antigenic repertoire. The vast majority of the strains belonging to this cluster express the O25b antigen and hence a specific gene (within the LPS synthesis locus) encoding for enzymes synthesizing this antigen is used for the identification of this clone (Clermont et al. J Antimicrob Chemother 2008 May; 61(5):1024-8). Alternatively, agglutination with the O25 typing sera can be used, in spite that the O antigen of this lineage differ from the classical O25 antigen (hence it had been termed O25b) as suggested by genetic differences. However, the O25 typing sera cannot distinguish between the mostly non-MDR O25 and the MDR O25b clones.

Rogers et al. (J Antimicrob Chemother 2011 January; 66(1):1-14) describe the detection of the E. coli O25b-ST131 strain by three major characteristics, i.e. its serogroup (O25b), its phylogenetic group (B2) and its ST (ST131). Each of these characteristics is disclosed to aid detection. A variety of molecular techniques is described, i.e. MLST, PCR-based rapid detection methods, repetitive sequence PCR and PFGE. Polyclonal antisera (raised against an O25a strain) including a variety of immunoglobulins have been used to determine the O25 antigen, not differentiating subtypes.

Jadhav et al. (PLOS ONE 2011; 6(3): e18063) describe the virulence characteristics and genetic affinities of strains which were positive for the O25b subgroup that is linked to the B2-O25b-ST131-CTX-M-15 virulent/multiresistant type. Human clinical isolates were analyzed and classified into serotypes and virulence marker profiles were obtained. O25 positive strains were identified by serotyping using polyclonal antisera against O-antigens—O1 to O173. The O25 positive strains were further subjected to genotyping by an allele-specific PCR targeting the rfbO25b subgroup germ locus.

Mora et al. (Int. J. Antimicrobial Agents 2011; 37(1): 16-21) describe the emergence of some clonal groups among CTX-M-14 producing E. coli clinical isolates, among them O25b: H4-B2-ST131. O typing was done with specific O antisera (polyclonal).

Clermont et al. (J Antimicrob Chemother 2008 May; 61(5):1024-8) discloses an allele-specific pabB PCR assay specific for O25b ST131 E. coli.

Szijarto et al, (FEMS Microbiol Lett 2012; 332:131-6) describe molecular typing of E. coli strain isolates based on the core structure of the LPS molecule. The core type of the isolates was determined by PCR using primers targeting genes in the core operon and specific to R1-4 and K-12 core types, respectively.

SUMMARY OF THE INVENTION

It is the objective of the present invention to provide for an antibody directed against of E. coli, in particular MDR strains, with improved specificity to be used for the prevention or therapy of E. coli infections caused by LPS O25b carrying strains. It is further the objective to provide means and methods that are capable of diagnosing E. coli bacteria, such as MDR strains, in a rapid and reliable manner.

The object is solved by the subject of the present invention.

According to the invention there is provided an isolated antibody that specifically binds to O25b antigen of E. coli strains comprising at least an antibody heavy chain variable region (VH), which comprises any of the CDR1 to CDR3 sequences as listed in FIG. 1, or functionally active CDR variants thereof.

According to the invention there is provided an isolated antibody that specifically binds to O25b antigen of E. coli strains comprising at least an antibody heavy chain variable region (VH), which comprises any of the CDR1 to CDR3 sequences as listed in Table 1, which are designated according to the numbering system of Kabat, or as listed in Table 2, which are designated according to the IMGT numbering system, or functionally active CDR variants thereof.

Specifically, the E. coli strains are MDR strains.

In the following unless indicated otherwise, reference is made to the CDR sequences as numbered according to Kabat, i.e. as determined according to Kabat nomenclature (see Kabat et al., Sequences of Proteins of Immunological Interest, 5^(th) Ed. Public Health Service, U.S. Department of Health and Human Services. (1991)), and in particular those CDR sequences as listed in Table 1 (SEQ ID 1-97). It is well understood that the invention and the scope of the claims shall also encompass the same antibodies and CDR, yet with a different numbering and designated CDR region, such as listed in Table 2 (SEQ ID 98-183, and SEQ ID 39), where CDR regions are defined according to the IMGT system (The international ImMunoGeneTics, Lefranc et al., 1999, Nucleic Acids Res. 27: 209-212).

Specifically, the antibody is

A)

selected from the group consisting of group members i) to xiv), wherein

i)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 1; and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 2; and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 3;

ii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 7; and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 8; and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 9;

iii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 11;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 12;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 13;

iv)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 17;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 18;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 19;

v)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 23;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 24;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 25;

vi)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 29;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 30;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 31;

vii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 34;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 35;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 36;

viii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 29;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 40;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 41;

ix)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 44;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 45;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 46;

x)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 50;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 51;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 52;

xi)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 50;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 55;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 56;

xii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 57;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 58;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 59;

xiii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 61;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 62;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 63;

xiv)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 66;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 67;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 68;

or

B) an antibody which is a functionally active variant of a parent antibody that is any of the group members of A, which comprises at least one functionally active CDR variant of any of the CDR1, CDR2 or CDR3 of the parent antibody.

Specifically, the functionally active variant is a functionally active CDR variant which comprises at least one point mutation in the parent CDR sequence, and comprises or consists of the amino acid sequence that has at least 60% sequence identity with the parent CDR sequence, preferably at least 70%, at least 80%, at least 90% sequence identity.

According to a specific aspect, the antibody of the invention comprises

-   -   a) a VH amino acid sequence selected from any of the VH         sequences as depicted in FIG. 2, preferably of the antibody         heavy chain (HC) amino acid sequence which is any of SEQ ID 184         to SEQ ID 231 or any of SEQ ID 312 to SEQ ID 315;     -   b) an antibody heavy chain (HC) amino acid sequence which is any         of SEQ ID 184 to SEQ ID 231 or any of SEQ ID 312 to SEQ ID 315;         or     -   c) an antibody heavy chain (HC) amino acid sequence which is any         of SEQ ID 184 to SEQ ID 231 or any of SEQ ID 312 to SEQ ID 315,         and which is further comprising a deletion of the C-terminal         amino acid and/or a Q1E point mutation, If the first amino acid         of the VH sequence is a Q.

For example, such functionally active variant of a parent antibody is a O25b-specific antibody which is specifically binding the O25b antigen only. Exemplary parent antibodies are listed in FIG. 1, group 1 antibodies, e.g. a humanized variant of the 8A1, 3E9 or 2A7 parent antibody such as listed in FIG. 2. Specifically, the VH or HC sequences of such variants may be substituted by VH and HC sequences of another variant, respectively, in particular where the other variant is any other variant of the same parent antibody.

According to a specific aspect, the antibody of the invention optionally further comprises an antibody light chain variable region (VL), which comprises any of the CDR4 to CDR6 sequences as listed in Table 1, which are designated according to the numbering system of Kabat, or as listed in Table 2, which are designated according to the IMGT numbering system, or functionally active CDR variants thereof.

Specifically, the antibody is

A)

selected from the group consisting of group members i) to xiv), wherein

i)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 4; and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 5; and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 6;

ii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 10;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 5; and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 6;

iii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 14;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 15;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 16;

iv)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 20;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 21;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 22;

v)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 26;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 27;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 28;

vi)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 20;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 33;

vii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 37;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 27;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 38;

viii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 42;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 43;

ix)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 47;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 48;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 49;

x)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 53;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 54;

xi)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 57;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 54;

xii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 26;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 27;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 60;

xiii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 64;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 65;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 38;

xiv)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 69;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 70;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 71;

or

B) an antibody which is a functionally active variant of a parent antibody that is any of the group members of A, which comprises at least one functionally active CDR variant of any of the CDR4, CDR5 or CDR6 of the parent antibody.

Specifically, the antibody comprises a VL amino acid sequence selected from any of the VL sequences as depicted in FIG. 2, preferably of an antibody light chain (LC) amino acid sequence which is any of SEQ ID 248 to SEQ ID 295 or any of SEQ ID 316 to SEQ ID 319, or comprising an antibody light chain (LC) amino acid sequence which is any of SEQ ID 248 to SEQ ID 295 or any of SEQ ID 316 to SEQ ID 319.

According to a specific aspect, the antibody of the invention is cross-specific to bind an epitope shared by the O25a and O25b antigens, e.g. with equal, more than equal, similar or different affinities.

Specifically, the antibody of the invention is cross-specific to bind the O25b and O25a antigens and/or preferentially binds to the O25b antigen relative to an O25a antigen of E. coli, preferably with a higher affinity as compared to binding the O25b antigen by a polyclonal serum raised against O25 (now known and herein referred to as O25a) E. coli strains as determined by immunoassay, compared to polyclonal typing serum raised against O25a strains, preferably wherein the antibody has at least equal affinity to both, the O25b and the O25a antigens, as determined by immunoassay, preferably immunoblotting, ELISA or other immunological methods.

Unless indicated as “cross-specific”, the antibody of the invention is herein understood as either the O25b specific, i.e. the antibody that specifically recognizes the O25b antigen only, e.g. any of the group 1 antibodies of Table 1, or the cross-specific antibody, i.e. the antibody that specifically recognizes an epitope shared between the O25b and O25a antigen, e.g. any of the group 2 antibodies of Table 1. Thus, the term “antibody of the invention” encompasses both, the O25b specific one and the O25b/O25a cross-specific one. The antibody of the invention is specifically further characterized that it does not cross-react with any other E. coli antigen, and/or the antibody binds to any other E. coli antigen with a lower affinity, e.g. where the Kd difference to preferentially bind the O25b antigen over other E. coli antigens (other than the O25b or O25a antigens) is at least 2 logs, preferably at least 3 logs.

Specifically, the cross-specific antibody is

A)

selected from the group consisting of group members i) to vii), wherein

i)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 72;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 73;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 74;

ii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 77;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 78;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 79;

iii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 81;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 82;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 83;

iv)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 84;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 85;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 86;

v)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 77;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 89;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 90;

vi)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 92;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 93;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 94;

vii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 95;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 96;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 97;

or

B) an antibody which is a functionally active variant of a parent antibody that is any of the group members of A, which comprises at least one functionally active CDR variant of any of the CDR1, CDR2 or CDR3 of the parent antibody.

Specifically, the antibody comprises

-   -   a) a VH amino acid sequence selected from any of the VH         sequences as depicted in FIG. 2, preferably of an antibody heavy         chain (HC) amino acid sequence which is any of SEQ ID 232 to SEQ         ID 247 or any of SEQ ID 312 to SEQ ID 315;     -   b) an antibody heavy chain (HC) amino acid sequence which is any         of SEQ ID 232 to SEQ ID 247 or any of SEQ ID 312 to SEQ ID 315;         or     -   c) an antibody heavy chain (HC) amino acid sequence which is any         of SEQ

ID 232 to SEQ ID 247 or any of SEQ ID 312 to SEQ ID 315, and which is further comprising a deletion of the C-terminal amino acid and/or a Q1E point mutation, if the first amino acid of the VH sequence is a Q.

For example, such functionally active variant of a parent antibody is a cross-specific antibody. Exemplary parent antibodies are listed in FIG. 1, group 2 antibodies, e.g. a humanized variant of the 4D5 parent antibody such as listed in FIG. 2. Specifically, the VH or HC sequences of such variants may be substituted by VH and HC sequences of another variant, respectively, in particular where the other variant is any other variant of the same parent antibody.

According to a specific aspect, the cross-specific antibody of the invention optionally further comprises an antibody light chain variable region (VL), which comprises any of the CDR4 to CDR6 sequences as listed in Table 1, which are designated according to the numbering system of Kabat, or as listed in Table 2, which are designated according to the IMGT numbering system, or functionally active CDR variants thereof, specifically including CDR sequences of any cross-specific antibody.

Specifically, the cross-specific antibody is

A)

selected from the group consisting of group members i) to vi), wherein

i)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 75;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 76;

ii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 75;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 80;

iii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 69;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 70;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 71;

iv)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 42;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 87;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 88;

v)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 37;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 27;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 91;

vi)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 42;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 88;

or

B) an antibody which is a functionally active variant of a parent antibody that is any of the group members of A, which comprises at least one functionally active CDR variant of any of the CDR4, CDR5 or CDR6 of the parent antibody.

Specifically, the functionally active variant is a functionally active CDR variant which comprises at least one point mutation in the parent CDR sequence, and comprises or consists of the amino acid sequence that has at least 60% sequence identity with the parent CDR sequence, preferably at least 70%, at least 80%, at least 90% sequence identity.

According to a specific aspect, the cross-specific antibody of the invention comprises a VL amino acid sequence selected from any of the VL sequences as depicted in FIG. 2, preferably of an antibody light chain (LC) amino acid sequence which is any of SEQ ID 296 to SEQ ID 311 or any of SEQ ID 316 to SEQ ID 319, or comprising an antibody light chain (LC) amino acid sequence which is any of SEQ ID 296 to SEQ ID 311 or any of SEQ ID 316 to SEQ ID 319.

According to a specific embodiment, the antibody of the invention specifically comprises

-   -   a) the CDR1-CDR6 sequences of any of the antibodies as listed in         Table 1; or     -   b) the VH and VL sequences of any of the antibodies as depicted         in FIG. 2; or     -   c) the HC and LC sequences of any of the antibodies as listed in         FIG. 2; or     -   d) which is a functionally active variant of a parent antibody         that is characterized by the sequences of a)-c),     -   preferably wherein         -   i. the functionally active variant comprises at least one             functionally active CDR variant of any of the CDR1-CDR6 of             the parent antibody; and/or         -   ii. the functionally active variant comprises at least one             point mutation in the framework region of any of the VH and             VL sequences and/or the HC and LC sequences of the parent             antibody, optionally comprising a Q1E point mutation, if the             first amino acid of the VH framework region (VH FR1) is a Q;     -   and further wherein         -   iii. the functionally active variant has a specificity to             bind the same epitope as the parent antibody; and/or         -   iv. the functionally active variant is a human, humanized,             chimeric, or murine and/or affinity matured variant of the             parent antibody.

According to a specific aspect, the antibody of the invention comprises CDR combinations as listed in Table 1, provided, that the antibody is still functionally active.

Specifically, the antibody of the invention comprises the CDR1-6 of any of the antibodies as listed in Table 1. However, according to an alternative embodiment, the antibody may comprise different CDR combinations, e.g. wherein an antibody as listed in Table 1 comprises at least one CDR sequence, such as 1, 2, 3, 4, 5, or 6 CDR sequences of one antibody and at least one further CDR sequence of a different antibody of any of the antibodies as listed in Table 1. According to a specific example, the antibody comprises 1, 2, 3, 4, 5, or 6 CDR sequences, wherein the CDR sequences are CDR combinations of more than 1 antibody, e.g. 2, 3, 4, 5, or 6 different antibodies. For example, the CDR sequences may be combined to preferably comprise 1, 2, or all 3 of CDR1-3 of any of the antibodies as listed in Table 1, and 1, 2, or all 3 of CDR4-6 of the same or any other antibody listed in Table 1.

It is herein specifically understood that the CDRs numbered CDR1, 2, and 3 represent the binding region of the VH domain, and CDR4, 5, and 6 represent the binding region of the VL domain.

According to a specific aspect, the antibody of the invention comprises any of the HC and LC amino acid sequence combinations as depicted in FIG. 2, or the binding site formed by such combination of HC and LC amino acid sequences. Alternatively, combinations of the immunoglobulin chains of two different antibodies may be used, provided, that the antibody is still functionally active. For example, the HC sequence of one antibody may be combined with an LC sequence of another antibody. According to further specific embodiments, any of the framework regions as provided in FIG. 2 may be employed as a framework to any of the CDR sequences and/or VH/VL combinations as described herein.

It is understood that the antibody of the invention optionally comprises such amino acid sequences of FIG. 2 with or without the respective signal sequence, or with alternative signal or leader sequences.

According to a specific aspect, each of the sequences of FIG. 2 may be terminally extended or deleted in the constant region, e.g. a deletion of one or more or the C-terminal amino acids.

Specifically, each of the HC sequences of FIG. 2 that comprises a C-terminal Lysine residue is preferably employed with a deletion of such C-terminal Lysine residue.

FIG. 2 shows different HC sequences and different LC sequences, and supports any HC/LC combination, thus a series of different HC/LC combinations for each of the parent antibodies. Therefore, specific variants of each parent antibody may include any HC/LC combination of each of the variants antibodies shown in FIG. 2 that derive from the same parent antibody.

In particular, FIG. 2 shows four different HC sequences and four different LC sequences which are variants of each of the parent antibodies 8A1, 3E9 (1G8), or 2A7 of group 1 antibodies, which specifically recognize the O25b antigen only, and of the parent antibody 4D5 of group 2 antibodies, which cross-specifically bind the O25b and O25a antigen. Sixteen different HC/LC combinations are shown for each of the parent antibodies.

In addition, FIG. 2 shows two further different HC sequences and two further different LC sequences which are variants of the parent antibody 3E9 (1G8) of group 1 antibodies, which specifically recognize the O25b antigen only.

In addition, FIG. 2 shows two further different HC sequences and two further different LC sequences which are variants of the parent antibody 4D5 of group 2 antibodies, which cross-specifically bind the O25b and O25a antigen.

The CDR sequences are identical to the respective CDR sequences as listed in FIG. 1: The CDR sequences of the parent 8A1, 1G8, 2A7 or 4D5 antibody are identical to those of the 8A1-1G8, 3E9-G11, 2A7-F1, and 4D5-D4 antibodies of FIG. 1, respectively.

Specifically, SEQ ID 184-SEQ ID 247 and SEQ ID 312-SEQ ID 315 show the HC sequences which include the VH amino acid sequences indicated in FIG. 2, each HC sequence being possibly N-terminally extended by a signal sequence. It is understood that the specific antibody comprises such VH or HC amino acid sequence with or without the respective signal sequence, or with alternative signal or leader sequences.

Specifically, SEQ ID 248-SEQ ID 311 and SEQ ID 316-SEQ ID 319 show the LC sequences which include the VL amino acid sequences indicated in FIG. 2, each LC sequence being possibly N-terminally extended by a signal sequence. It is understood that the specific antibody comprises such VL or LC amino acid sequence with or without the respective signal sequence, or with alternative signal or leader sequences.

The invention further provides for a method of producing functionally active antibody variants of a parent antibody which is any of the antibodies of the invention, e.g. an antibody as listed in Table 1, or comprising any of the HC and LC amino acid sequence combinations as depicted in FIG. 2, or comprising the binding site formed by such combination of HC and LC amino acid sequences, which method comprises engineering at least one point mutation in any of the framework regions (FR) or constant domains, or complementarity determining regions (CDR1 to CDR6) to obtain a variant antibody, and determining the functional activity of the variant antibody, specifically by the affinity to bind the O25b with a Kd of less than 10⁻⁶M, preferably less than 10⁻⁷M, or less than 10⁻⁸M, or less than 10⁻⁹M, even less than 10⁻¹⁰M, or less than 10⁻¹¹M, e.g. with an affinity in the picomolar range. Upon determining the functional activity, the functionally active variants are selected for further use and optionally for production by a recombinant production method.

Preferred CDR variants include mutations of motifs that are prone to glycosylation or deamidation. For example, in the N-linked glycosylation motif NXS/T in any of the CDR sequences, where X is any amino acid, the ‘N’ in this motif may be mutated to any other different amino acid, preferably ‘Q’, ‘S’ or ‘D’ to remove the potential for glycosylation. Further examples refer to the amino acid motifs NG or NN, in any of the CDR sequences, which may be prone to deamidation of asparagines to aspartic acid. Asparagine within other motifs is less prone to deamidation.

For example, the amino acid motif SNG found in the VL CDR1 (CDR4) of 4D5 can be prone to deamidation of asparagine to aspartic acid. Therefore, “polishing” mutation of the ‘N’ in the SNG motif in the VL CDR1 of mAb 4D5 would be mutated to any other different amino acid, preferably ‘Q’, ‘S’ or ‘D’ in order to remove the potential deamidation site.

According to a specific aspect, the variant antibody binds the same epitope as the parent antibody.

According to a further specific aspect, the variant antibody comprises the same binding site as the parent antibody.

Functionally active variant antibodies may differ in any of the VH or VL sequences, or share the common VH and VL sequences, and comprise modifications in the respective FR. The variant antibody derived from the parent antibody by mutagenesis may be produced a methods well-known in the art.

Exemplary parent antibodies are described in the examples section below and in FIG. 1 (Table 1) and FIG. 2. Specifically, the antibody is a functionally active derivative of a parent antibody as listed in Table 1. Variants with one or more modified CDR sequences, and/or with one or more modified FR sequences, such as sequences of FR1, FR2, FR3 or FR4, or a modified constant domain sequence may be engineered.

For example, functionally active variant antibodies are provided according to the invention and listed in FIG. 2, which are derived from parent antibodies listed in Table 1 and have been obtained by mutagenesis, specifically by affinity maturation and/or humanization. Though the variant antibodies of FIG. 2 still share the common VH and VL sequences of the respective parent antibody, it is feasible that also variant VH and VL chains, e.g. with modifications in the respective FR or CDR sequences may be produced, which are functionally active.

Exemplary variant antibodies of a parent antibody comprise at least one point mutation in any of the CDR1-CDR6, and/or at least one point mutation in the FR region, preferably wherein the antibody has a specificity to bind the same epitope as the parent antibody.

In certain aspects, the invention provides for such functionally active variant antibodies, preferably monoclonal antibodies, most preferably human antibodies, comprising a heavy chain and a light chain, wherein any of the light chain or VL variable region or the respective CDRs comprises an amino acid sequence as derived from a parent antibody, which is the antibody designated 8D5-1G10 or 4D5-D4 or any other antibody as listed in Table 1 or FIG. 2, by modification of at least one FR or CDR sequences.

The antibody designated 4D5-D4 and listed in Table 1 turned out to comprise the same CDR sequences as the antibody 8D10-C8 (which is characterized by the deposited material as indicated below), and even the same VH/VL sequences, however, differ in the constant domains or region, i.e. comprises at least one modification in any of the constant domains.

According to a specific embodiment, the antibody of the invention is any other antibody except the antibodies designated 8D5-1G10 or 8D10-C8. Such antibodies are specifically understood to be composed of one or two of the variable domains VH/VL only, and which are defined by the deposited VH/VL material as further described herein. However, specific variants of the antibodies designated 8D5-1G10 or 8D10-C8 are specifically included in the subject of the present claims, including, but not limited to, CDR variants, FR variants, murine, chimeric, humanized or human variants, or any antibody domain combination other than a combination composed of the one or two of the VH/VL combination, including full-length antibodies of various types, Fab, scFv, etc.

Specific embodiments refer to the 4D5-D4 (4D5) or 8A1-1G8 (8A1) antibodies which are characterized by the CDR sequences and the variable domains of the respective antibody referred to in FIG. 1 and further specified in FIG. 2, which antibodies include variable and constant domains, e.g. are full-length antibodies, and which are murine, chimeric, humanized or human antibodies.

However, the antibody designated as 8D5-1G10 or 8D10-C8 may be used as a parent antibody to engineer a functionally active variant thereof. Specifically, the antibody designated 8D5-1G10 or 8D10-C8 or any functionally active variant thereof may be produced employing the sequences as provided herein by recombinant means, optionally with further immunoglobulin sequences, e.g. to produce an IgG antibody. Specifically, a functionally active variant of such antibody designated as 8D5-1G10 or 8D10-C8 may be produced by modification of at least one FR or CDR sequences.

According to a specific aspect, the invention provides for an isolated monoclonal antibody that specifically binds to O25b antigen of multi drug resistant (MDR) E. coli strains which comprises the antigen-binding site of antibody 8D5-1G10, or which is derived from the antibody 8D5-1G10, or a functionally active variant of the antibody 8D5-1G10, preferably wherein the antibody 8D5-1G10 is characterized by

-   -   a) the variable region of the antibody light chain produced by         the host cell deposited under DSM 26763; and/or     -   b) the variable region of the antibody heavy chain produced by         the host cell deposited under DSM 26762;     -   c) or a functionally active variant of (a) and/or (b) is         employed.

Specifically, the antibody designated as 8D5-1G10 is composed of an antibody light chain comprising the variable region encoded by the coding sequence of the plasmid comprised in the E. coli host cell deposited under DSM 26763, and an antibody heavy chain comprising the variable region encoded by the coding sequence of the plasmid comprised in the E. coli host cell deposited under DSM 26762.

According to another specific aspect, the invention provides for an isolated monoclonal antibody which is cross-specific to bind an epitope shared by the O25a and O25b antigens, and which comprises the antigen-binding site of antibody 8D10-C8, or which is derived from the antibody 8D10-C8, or a functionally active variant of the antibody 8D10-C8, preferably wherein the antibody 8D10-C8 is characterized by

-   -   a) the variable region of the antibody light chain produced by         the host cell deposited under DSM 28171; and/or     -   b) the variable region of the antibody heavy chain produced by         the host cell deposited under DSM 28172;     -   c) or a functionally active variant of (a) and/or (b) is         employed.

Specifically, the antibody designated as 8D10-C8 is composed of an antibody light chain comprising the variable region encoded by the coding sequence of the plasmid comprised in the E. coli host cell deposited under DSM 28171, and an antibody heavy chain comprising the variable region encoded by the coding sequence of the plasmid comprised in the E. coli host cell deposited under DSM 28172.

Specifically, the antibody comprises a functionally active CDR variant of any of the CDR sequences as listed in Table 1, wherein the functionally active CDR variant comprises at least one of

-   -   a) 1, 2, or 3 point mutations in the parent CDR sequence; and/or     -   b) 1 or 2 point mutations in any of the four C-terminal or four         N-terminal, or tour centric amino acid positions of the parent         CDR sequence; and/or     -   c) at least 60% sequence identity with the parent CDR sequence.

Specifically, the functionally active variant antibody comprises at least one of the functionally active CDR variants of the invention. Specifically, the functionally active variant antibody comprising one or more of the functionally active CDR variants has a specificity to bind the same epitope as the parent antibody.

Specifically, the functionally active variant is a CDR variant, e.g. which comprises a CDR, more specifically a CDR loop sequence, with an amino acid sequence having at least 60% sequence identity, preferably at least 70%, 80% or 90% sequence identity.

According to a specific aspect, the at least one point mutation is any of an amino acid substitution, deletion and/or insertion of one or more amino acids.

Specifically, the functionally active variant differs from the parent antibody in at least one point mutation in the amino acid sequence, preferably in the CDR, wherein the number of point mutations in each of the CDR amino acid sequences is either 0, 1, 2 or 3.

Specifically, the antibody is derived from such antibodies, employing the respective CDR sequences, or CDR mutants, including functionally active CDR variants, e.g. with 1, 2 or 3 point mutations within one CDR loop, e.g. within a CDR length of 5-18 amino acids, e.g. within a CDR region of 5-15 amino acids or 5-10 amino acids. Alternatively, there may be 1 to 2 point mutations within one CDR loop, e.g. within a CDR length of less than 5 amino acids, to provide for an antibody comprising a functionally active CDR variant. Specific CDR sequences might be short, e.g. the CDR2 or CDR5 sequences. According to a specific embodiment, the functionally active CDR variant comprises 1 or 2 point mutations in any CDR sequence consisting of less than 4 or 5 amino acids.

According to a specific aspect, the antibody of the invention comprises CDR and framework sequences, wherein at least one of the CDR and framework sequences includes human, humanized, chimeric, murine or affinity matured sequences, preferably wherein the framework sequences are of an IgG antibody, e.g. of an IgG1, IgG2, IgG3, or IgG4 subtype, or of an IgA1, IgA2, IgD, IgE, or IgM antibody.

Specific antibodies are provided as framework mutated antibodies, e.g. to improve manufacturability or tolerability of a parent antibody, e.g. to provide an improved (mutated) antibody which has a low immunogenic potential, such as humanized antibodies with mutations in any of the CDR sequences and/or framework sequences as compared to a parent antibody.

Further specific antibodies are provided as CDR mutated antibodies, e.g. to improve the affinity of an antibody and/or to target the same epitope or epitopes near the epitope that is targeted by a parent antibody (epitope shift).

Accordingly, any of the antibodies as listed in Table 1 or FIG. 2 may be used as parent antibodies to engineer improved versions.

According to a specific aspect, the antibody of the invention has an affinity to bind the O25b antigen with a Kd of less than 10⁻⁸M, preferably less than 10⁻⁷M or less than 10⁻⁸M. Affinity maturated variants typically have an affinity to bind the O25b antigen with a Kd of less than 10⁻⁸M.

Specifically, the antibody of the invention preferentially binds to the O25b antigen relative to the O25a antigen of E. coli, or at least with equal affinity towards both antigens.

According to a specific embodiment, the antibody has at least two-fold greater affinity for binding the O25b antigen as compared to the O25a antigen, specifically with at least two-fold difference, or at least three-fold, at least four-fold, at least 5-fold, or even at least 10-fold difference in binding either the O25b or the O25a antigen, e.g. difference in affinity and/or avidity.

According to a specific aspect the specific binding to O25b is characterized by the greater affinity for binding the O25b antigen as compared to binding the O25b antigen by a polyclonal serum raised against O25 or O25a E. coli strains as determined by immunoassay, preferably immunoblotting, ELISA or other immunological methods. The higher binding affinity is specifically with at least two-fold difference, or at least three-fold, at least four-fold, at least 5-fold, or even at least 10-fold difference.

Specifically, the O25b antigen as targeted by the antibody of the invention is prevalent in one or more, and more specifically present in the vast majority of ST131 strains.

Specifically, the epitope recognized by the antibody is present on the surface of encapsulated and non-encapsulated ST131-O25b:H4 strains, e.g. mutant strains.

According to a further specific aspect, the antibody exhibits in vitro bactericidal potency in a serum sample comprising live wild-type MDR E. coli strains.

According to a further specific aspect, the antibody stimulates uptake of live wild-type MDR E. coli strains by phagocytic cells in vitro.

According to a further specific aspect, the antibody neutralizes endotoxic effect of specific LPS molecules in vitro.

Specifically, the antibody is a full-length monoclonal antibody, an antibody fragment thereof comprising at least one antibody domain incorporating the antigen binding site, or a fusion protein comprising at least one antibody domain incorporating the antigen binding site. Preferably, the antibody is selected from the group consisting of murine, chimeric, humanized or human antibodies, heavy-chain antibodies, Fab, Fd, scFv and single-domain antibodies like VH, VHH or VL, preferably a human IgG1 antibody.

According to a further specific aspect, the antibody has a binding site of a full-length monoclonal antibody or an antibody fragment thereof comprising at least one antibody domain incorporating a binding site, which antibody is preferably an antibody selected from the group consisting of murine, lama, rabbit, goat, cow, chimeric, humanized or human antibodies, heavy-chain antibodies, Fab, Fd, scFv and single-domain antibodies like VH, VHH or VL, preferably a human IgG antibody or a murine IgG antibody.

According to the invention, the antibody of the invention is specifically provided for medical, diagnostic or analytical use.

According to a specific aspect, the antibody of the invention is provided for use in treating a subject at risk of or suffering from an E. coli infection, in particular an infection by an MDR E. coli strain, comprising administering to the subject an effective amount of the antibody to limit the infection in the subject or to ameliorate a disease condition resulting from said infection, preferably for treatment or prophylaxis of pyelonephritis, secondary bacteremia, sepsis, peritonitis, meningitis, and ventilator-associated pneumonia.

Accordingly, the invention specifically provides for a method of treatment, wherein a subject at risk of or suffering from an E. coli infection is treated by administering to the subject an effective amount of the antibody.

Specifically, the antibody is provided for bactericidal killing of MDR E. coli, preferably a ST131-O25b:H4 strain irrespective of capsular polysaccharide expressed by the strain.

According to a specific aspect, immunotherapy using the antibody of the invention may effectively protect against live bacterial challenge, e.g. as determined in various animal models.

The antibody may specifically neutralize lethal endotoxemia. Such functional activity may be determined in an appropriate in vivo model (challenge with purified LPS).

The antibody is specifically effective against MDR E. coli by complement-mediated killing, e.g. as determined by an in vitro serum bactericidal assay (SBA), e.g. with at least 20% killing of bacteria above the control samples (no antibody or irrelevant control mAb added).

The antibody is specifically effective against MDR E. coli by antibody mediated phagocytosis, e.g. as determined by an in vitro opsonophagocytotic killing assay (OPK), e.g. with at least 20% uptake of input bacteria or 20% lower end CFU count above the control samples (no antibody or irrelevant control mAb added).

The antibody is specifically effective against MDR E. coli by neutralizing endotoxin functions, e.g. as determined by an in vitro LAL assay, or toll-like receptor 4 (TLR4) reporter assay e.g. with at least 20% reduction in endotoxin activities in comparison to control samples (no antibody or irrelevant control mAb added).

The invention further provides for a pharmaceutical preparation comprising the antibody of the invention, preferably comprising a parenteral or mucosal formulation, optionally containing a pharmaceutically acceptable carrier or excipient.

Such pharmaceutical composition may contain the antibody as the sole active substance, or in combination with other active substances, or a cocktail of active substances, such as a combination or cocktail of at least two or three different antibodies.

According to a specific aspect, the antibody of the invention is provided for diagnostic use to determine E. coli infection or bacteremia in a subject caused by an E. coli strain, in particular infection caused by an MDR strain expressing the LPS O25b, such as upper and lower urinary tract infections, including cystitis or urethritis, ascending or hematogenous pyelonephritis, especially in diabetic patients, as well as with bacteremia, sepsis, peritonitis, or intestinal colonization.

Specifically, the antibody is provided for use according to the invention, wherein a systemic infection with MDR E. coli in a subject is determined ex vivo by contacting a sample of body fluid of said subject with the antibody, wherein a specific immune reaction of the antibody determines the infection.

Specifically, a sample of body fluid is tested for the specific immune reaction, which sample is selected from the group consisting of urine, blood, blood isolates or blood culture, aspirate, sputum, lavage fluid of intubated subjects and stool.

Specifically, the diagnostic use according to the invention refers to determining the serotype of E. coli in vitro from a pure E. coli culture recovered from a clinical specimen.

According to a further aspect, the invention provides for a diagnostic preparation of an antibody of the invention, optionally containing the antibody with a label and/or a further diagnostic reagent with a label, such as a reagent specifically recognizing the antibody or an immune complex of the antibody with the respective target antigen, and/or a solid phase to immobilize at least one of the antibody and the diagnostic reagent.

The invention further provides for a diagnostic preparation comprising of the antibody of the invention, comprising the antibody and a further diagnostic reagent in a composition or a kit of parts, comprising the components

-   -   a) the antibody; and     -   b) the further diagnostic reagent;     -   c) and optionally a solid phase to immobilize at least one of         the antibody and the diagnostic reagent.

The invention further provides for a method of diagnosing E. coli infection or bacteremia in a subject caused by an E. coli strain, comprising

-   -   a) providing an antibody of the invention, and     -   b) detecting if the antibody specifically immunoreacts with the         O25b antigen, e.g. by immunoreaction with O25b antigen only or         by cross-reactive immunoreaction to react with O25b and O25a, in         a biological sample of the subject, e.g. blood or serum, to be         tested, preferably by an agglutination test, thereby diagnosing         MDR E. coli infection or bacteremia.

Suitable biological samples of the subject may be specifically selected from the group consisting of blood, serum, blood isolates or blood culture, urine, aspirate, sputum, lavage fluid of intubated subjects and stool.

Preferred diagnostic assays of the invention comprise the antibody of the invention immobilized on a solid phase, e.g. latex beads, gold particles, etc., e.g. to test agglutination by the antibody of bacteria expressing O25b antigen or free (or isolated) O25b antigen obtained from a sample to be tested.

Some diagnostic assays may involve two different antibodies with different specificity and/or affinity to bind O25b and/or O25a, so to possibly differentiate between the O25b and O25a antigens.

According to a specific aspect, the invention provides for companion diagnostics to determine the infection of a subject with E. coli, in particular with MDR E. coli, by the diagnostics of the invention or the diagnostic method of the invention, to provide for the basis of treatment with a therapeutic against such infection, e.g. employing immunotherapy, such as treating with an antibody of the invention.

According to a specific aspect, the invention provides for a sensitive bedside diagnostics to diagnose infection of a subject with MDR E. coli, in particular with MDR E. coli, by determining free LPS, e.g. from clinical specimen where the amount of live bacteria is limited. The sensitivity of such assay is specifically less than 100 ng preferably less than 10 ng of LPS.

The invention further provides for an isolated nucleic acid encoding an antibody of the invention.

The invention further provides for an expression cassette or a plasmid comprising a coding sequence to express

-   -   a) a VH and/or VL of an antibody of the invention; or     -   b) or a HC and/or LC of an antibody of the invention.

The invention further provides for a host cell comprising an expression cassette or a plasmid of the invention.

Specifically, a plasmid and a host cell are excluded, which material is deposited under DSM 26763 or DSM 26762. Such deposits are E. coli host cells transformed with a plasmid, wherein the host cell deposited under DSM 26763 is transformed with the plasmid comprising a nucleotide sequence encoding the antibody light chain designated 8D5-1G10-LC; and the host cell deposited under DSM 26762 is transformed with the plasmid comprising a nucleotide sequence encoding the antibody heavy chain designated 8D5-1G10-HC.

Specifically, further excluded is a plasmid and a host cell, which material is deposited under DSM 28171 or DSM 28172. Such deposits are E. coli host cells transformed with a plasmid, wherein the host cell deposited under DSM 28171 is transformed with the plasmid comprising a nucleotide sequence encoding the antibody light chain designated 8D10-C8-LC; and the host cell deposited under DSM 28172 is transformed with the plasmid comprising a nucleotide sequence encoding the antibody heavy chain designated 8D10-C8-HC.

The invention further provides for a method of producing an antibody of the invention, wherein a host cell of the invention is cultivated or maintained under conditions to produce said antibody.

According to a further aspect, the invention provides for a method of producing an antibody of the invention, comprising

a) immunizing a non-human animal with the O25b antigen of E. coli and isolating B-cells producing antibodies;

b) forming immortalized cell lines from the isolated B-cells;

c) screening the cell lines to identify a cell line producing a monoclonal antibody that specifically binds to the O25b antigen and optionally the O25a antigen, e.g. wherein preferential binding to O25b as compared to O25a is determined; and

d) producing the monoclonal antibody, or a humanized or human form of the antibody, or a derivative thereof with the same epitope binding specificity as the monoclonal antibody.

FIGURES

FIG. 1: Table 1 including CDR sequences of O25b specific antibodies (group 1 antibodies, binding to O25b only), and of O25b/O25a cross-specific antibodies (group 2 antibodies) CDR region identified according to the Kabat system; and Table 2 listing the same antibodies designating the CDR region according to the IMGT system. The nomenclature as used in Tables 1 and 2 shall have the following meaning:

VH CDR1=CDR1

VH CDR2=CDR2

VH CDR3=CDR3

VL CDR1=CDR4

VL CDR2=CDR5

VL CDR3=CDR6

FIG. 2: HC and LC sequence information of humanized variants of O25b specific antibodies of group 1 (FIG. 1), i.e. of parent antibodies 8A1, 3E9, and 2A7, wherein the variants are numbered 1-16 of the parent antibody 8A1, and numbered 1-18 of the parent antibody 3E9, and numbered 1-16 of the parent antibody 2A7; and HC and LC sequence information of humanized variants of a O25b and O25a cross-specific antibody of group 2 (FIG. 1), which is the parent antibody 4D5, wherein the variants are numbered 1-18.

FIG. 3:

FIG. 3i ): reactivity of different O25b-specific (with or without cross-reactivity to O25a antigen) mAbs as well as LPS core-specific (i.e. cross-reactive to all E. coli LPS molecules) mAb WN1 as control to purified O25a, O25b, and O55 LPS molecules in an immunoblot assay.

FIG. 3 ii): Immunoblots with O25-specific mAbs. Separated purified LPS of types O25a, O25b, and O55 were reacted with chimeric or humanized O25b-specific mAbs and the LPS-core specific (i.e. cross-reactive) WN-1 murine mAb as control.

FIG. 4:

FIG. 4i ): Affinity measurements of different O25b mAbs as assessed by ForteBio using biotinylated O25b PS antigen bound to streptavidin tips.

FIG. 4 ii): Biolayer inferometry (BLI) measurements. Binding of O25b mAbs to the O25b polysaccharide expressed as affinity, association and dissociation constants, measured in ForteBio.

FIG. 5:

FIG. 5i ): Surface staining of different E. coli strains expressing O25b, O25a, or O2 antigens by O25b-specific (with or without cross-reactivity to O25a antigen) mAbs.

FIG. 5 ii): ST131:O25b strain 3O grown either in LB (A) or in human serum (B) were stained with O25b-specific mAbs at a concentration range of 0.025-40 μg/ml. Additionally a panel of ST131 strains belonging to different pulsotypes were tested for surface staining by three O25b specific mAbs at a concentration of 40 μg/ml (C).

FIG. 6: Protection against bacterial challenge. Prophylactic protective efficacy of O25b-reactive chimeric (i) or humanized (ii) mAbs as well as an isotype matched control mAb was tested in a murine model of bacteremia. 100 μg of mAbs were injected i.p. 24 h prior to a lethal challenge with ST131 strain 81009 administered intavenously. Lethality was monitored daily.

FIG. 7:

FIG. 7i ): Serum bactericidal assay. Complement dependent bacterial killing mediated by the O25b specific mAbs was assessed as reduction of CFU after the 3 h incubation period relative to the initial bacterial number.

FIG. 7 ii): Serum bactericidal assay. Two different ST131:O25b strains were grown in LB (panels A, B and D) to mid-log phase. Following washing bacteria were incubated with 2.5 μg/ml of humanized (A, and B) or chimeric (D) mAbs for 3 h. Alternatively, strain 81009 was grown in human serum and incubated with 10 ug/ml of mAbs for 5 h (panel C). Number of surviving bacteria was determined by plating. Bactericidal activity is expressed as percent killing relative to control (no antibody) incubation.

FIG. 8: Protection in an endotoxaemia model. Groups of 5 mice were passive immunized with 100 μg (panels A and B) or 25 μg (panel C) of mAbs i.p. On the next day, mice were sensitized with 20 mg/mouse of D-GalN (i.p.) and simultaneously challenged with a lethal dose of purified O25b LPS (i.v.). Survival was monitored daily.

FIG. 9: In vitro endotoxin neutralization assay. The TLR-4 signalling of purified O25b LPS was assessed in the HEK-Blue assay (panel A). Dose dependent neutralizing potential of a representative O25b-specific mAb is shown in comparison to polymixin B (panel B). Neutralizing capacity expressed as IC₅₀ concentration of several humanized and chimeric O25b-specific mAbs determined in this setup is summarized on panel C.

FIG. 10: (a): Structure of the repeating unit of E. coli O25b antigen. (b): structure of the repeating unit of E. coli O25a (Kenne L, Lindberg B, Madden J K, Lindberg A A, Gemski P Jr. Structural studies of the Escherichia coli O-antigen 25. Carbohydr Res. 28; 122(2):249-56, 1983).

DETAILED DESCRIPTION

The term “antibody” as used herein shall refer to polypeptides or proteins that consist of or comprise antibody domains, which are understood as constant and/or variable domains of the heavy and/or light chains of immunoglobulins, with or without a linker sequence. Polypeptides are understood as antibody domains, if comprising a beta-barrel structure consisting of at least two beta-strands of an antibody domain structure connected by a loop sequence. Antibody domains may be of native structure or modified by mutagenesis or derivatization, e.g. to modify the antigen binding properties or any other property, such as stability or functional properties, such as binding to the Fc receptors FcRn and/or Fcgamma receptor.

The antibody as used herein has a specific binding site to bind one or more antigens or one or more epitopes of such antigens, specifically comprising a CDR binding site of a single variable antibody domain, such as VH, VL or VHH, or a binding site of pairs of variable antibody domains, such as a VL/VH pair, an antibody comprising a VL/VH domain pair and constant antibody domains, such as Fab, F(ab′), (Fab)₂, scFv, Fv, or a full length antibody.

The term “antibody” as used herein shall particularly refer to antibody formats comprising or consisting of single variable antibody domain, such as VH, VL or VHH, or combinations of variable and/or constant antibody domains with or without a linking sequence or hinge region, including pairs of variable antibody domains, such as a VL/VH pair, an antibody comprising or consisting of a VL/VH domain pair and constant antibody domains, such as heavy-chain antibodies, Fab, F(ab′), (Fab)₂, scFv, Fd, Fv, or a full-length antibody, e.g. of an IgG type (e.g., an IgG1, IgG2, IgG3, or IgG4 subtype), IgA1, IgA2, IgD, IgE, or IgM antibody. The term “full length antibody” can be used to refer to any antibody molecule comprising at least most of the Fc domain and other domains commonly found in a naturally occurring antibody monomer. This phrase is used herein to emphasize that a particular antibody molecule is not an antibody fragment.

The term “antibody” shall specifically include antibodies in the isolated form, which are substantially free of other antibodies directed against different target antigens or comprising a different structural arrangement of antibody domains. Still, an isolated antibody may be comprised in a combination preparation, containing a combination of the isolated antibody, e.g. with at least one other antibody, such as monoclonal antibodies or antibody fragments having different specificities.

The term “antibody” shall apply to antibodies of animal origin, including human species, such as mammalian, including human, murine, rabbit, goat, lama, cow and horse, or avian, such as hen, which term shall particularly include recombinant antibodies which are based on a sequence of animal origin, e.g. human sequences.

The term “antibody” further applies to chimeric antibodies with sequences of origin of different species, such as sequences of murine and human origin.

The term “chimeric” as used with respect to an antibody refers to those antibodies wherein one portion of each of the amino acid sequences of heavy and light chains is homologous to corresponding sequences in antibodies derived from a particular species or belonging to a particular class, while the remaining segment of the chain is homologous to corresponding sequences in another species or class. Typically the variable region of both light and heavy chains mimics the variable regions of antibodies derived from one species of mammals, while the constant portions are homologous to sequences of antibodies derived from another. For example, the variable region can be derived from presently known sources using readily available B-cells or hybridomas from non-human host organisms in combination with constant regions derived from, for example, human cell preparations.

The term “antibody” may further apply to humanized antibodies.

The term “humanized” as used with respect to an antibody refers to a molecule having an antigen binding site that is substantially derived from an immunoglobulin from a non-human species, wherein the remaining immunoglobulin structure of the molecule is based upon the structure and/or sequence of a human immunoglobulin. The antigen binding site may either comprise complete variable domains fused onto constant domains or only the complementarity determining regions (CDR) grafted onto appropriate framework regions in the variable domains. Antigen-binding sites may be wild-type or modified, e.g. by one or more amino acid substitutions, preferably modified to resemble human immunoglobulins more closely. Some forms of humanized antibodies preserve all CDR sequences (for example a humanized mouse antibody which contains all six CDRs from the mouse antibody). Other forms have one or more CDRs which are altered with respect to the original antibody.

The term “antibody” further applies to human antibodies.

The term “human” as used with respect to an antibody, is understood to include antibodies having variable and constant regions derived from human germline immunoglobulin sequences. The human antibody of the invention may include amino acid residues not encoded by human germline immunoglobulin sequences (e.g., mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo), for example in the CDRs. Human antibodies include antibodies isolated from human immunoglobulin libraries or from animals transgenic for one or more human immunoglobulin.

The term “antibody” specifically applies to antibodies of any class or subclass. Depending on the amino acid sequence of the constant domain of their heavy chains, antibodies can be assigned to the major classes of antibodies IgA, IgD, IgE, IgG, and IgM, and several of these may be further divided into subclasses (isotypes), e.g., IgG1, IgG2, IgG3, IgG4, IgA1, and IgA2.

The term further applies to monoclonal or polyclonal antibodies, specifically a recombinant antibody, which term includes all antibodies and antibody structures that are prepared, expressed, created or isolated by recombinant means, such as antibodies originating from animals, e.g. mammalians including human, that comprises genes or sequences from different origin, e.g. murine, chimeric, humanized antibodies, or hybridoma derived antibodies. Further examples refer to antibodies isolated from a host cell transformed to express the antibody, or antibodies isolated from a recombinant, combinatorial library of antibodies or antibody domains, or antibodies prepared, expressed, created or isolated by any other means that involve splicing of antibody gene sequences to other DNA sequences.

It is understood that the term “antibody” also refers to derivatives of an antibody, in particular functionally active derivatives. An antibody derivative is understood as any combination of one or more antibody domains or antibodies and/or a fusion protein, in which any domain of the antibody may be fused at any position of one or more other proteins, such as other antibodies, e.g. a binding structure comprising CDR loops, a receptor polypeptide, but also ligands, scaffold proteins, enzymes, toxins and the like. A derivative of the antibody may be obtained by association or binding to other substances by various chemical techniques such as covalent coupling, electrostatic interaction, di-sulphide bonding etc. The other substances bound to the antibody may be lipids, carbohydrates, nucleic acids, organic and inorganic molecules or any combination thereof (e.g. PEG, prodrugs or drugs). In a specific embodiment, the antibody is a derivative comprising an additional tag allowing specific interaction with a biologically acceptable compound. There is not a specific limitation with respect to the tag usable in the present invention, as far as it has no or tolerable negative impact on the binding of the antibody to its target. Examples of suitable tags include His-tag, Myc-tag, FLAG-tag, Strep-tag, Calmodulin-tag, GST-tag, MBP-tag, and S-tag. In another specific embodiment, the antibody is a derivative comprising a label. The term “label” as used herein refers to a detectable compound or composition which is conjugated directly or indirectly to the antibody so as to generate a “labeled” antibody. The label may be detectable by itself, e.g. radioisotope labels or fluorescent labels, or, in the case of an enzymatic label, may catalyze chemical alteration of a substrate compound or composition which is detectable.

The preferred derivatives as described herein are functionally active with regard to the antigen binding, preferably which have a potency to combat MDR E. coli and its endotoxin, e.g. as determined in an SBA, OPK or LAL assay, or to protect against bacterial challenge or to neutralize lethal endotoxemia.

Specifically, an antibody derived from an antibody of the invention may comprise at least one or more of the CDR regions or CDR variants thereof being functionally active in differentially binding to the O25b antigen, e.g. specifically or selectively binding the O25b antigen.

Antibodies derived from a parent antibody or antibody sequence, such as a parent CDR or FR sequence, are herein particularly understood as mutants or variants obtained by e.g. in silico or recombinant engineering or else by chemical derivatization or synthesis.

It is understood that the term “antibody” also refers to variants of an antibody, including antibodies with functionally active CDR variants of a parent CDR sequence, and functionally active variant antibodies of a parent antibody.

Specifically, an antibody derived from an antibody of the invention may comprise at least one or more of the CDR regions or CDR variants thereof, e.g. at least 3 CDRs of the heavy chain variable region and/or at least 3 CDRs of the light chain variable region, with at least one point mutation in at least one of the CDR or FR regions, or in the constant region of the HC or LC, being functionally active, e.g. specifically binding the O25b antigen and optionally cross-specifically binding the O25a antigen.

The term “variant” shall particularly refer to antibodies, such as mutant antibodies or fragments of antibodies, e.g. obtained by mutagenesis methods, in particular to delete, exchange, introduce inserts into a specific antibody amino acid sequence or region or chemically derivatize an amino acid sequence, e.g. in the constant domains to engineer the antibody stability, effector function or half-life, or in the variable domains to improve antigen-binding properties, e.g. by affinity maturation techniques available in the art. Any of the known mutagenesis methods may be employed, including point mutations at desired positions, e.g. obtained by randomization techniques. In some cases positions are chosen randomly, e.g. with either any of the possible amino acids or a selection of preferred amino acids to randomize the antibody sequences. The term “mutagenesis” refers to any art recognized technique for altering a polynucleotide or polypeptide sequence. Preferred types of mutagenesis include error prone PCR mutagenesis, saturation mutagenesis, or other site directed mutagenesis.

The term “variant” shall specifically encompass functionally active variants.

The term “functionally active variant” of a CDR sequence as used herein, is understood as a “functionally active CDR variant”, and the “functionally active variant” of an antibody as used herein, is understood as “functionally active antibody variant”. The functionally active variant means a sequence resulting from modification of this sequence (a parent antibody or a parent sequence) by insertion, deletion or substitution of one or more amino acids, or chemical derivatization of one or more amino acid residues in the amino acid sequence, or nucleotides within the nucleotide sequence, or at either or both of the distal ends of the sequence, e.g. in a CDR sequence the N-terminal and/or C-terminal 1, 2, 3, or 4 amino acids, and/or the centric 1, 2, 3, or 4 amino acids (i.e. in the midst of the CDR sequence), and which modification does not affect, in particular impair, the activity of this sequence. In the case of a binding site having specificity to a selected target antigen, the functionally active variant of an antibody would still have the predetermined binding specificity, though this could be changed, e.g. to change the fine specificity to a specific epitope, the affinity, the avidity, the Kon or Koff rate, etc. For example, an affinity matured antibody is specifically understood as a functionally active variant antibody. Hence, the modified CDR sequence in an affinity matured antibody is understood as a functionally active CDR variant.

Specifically, the functionally active variants of an antibody of the invention have the potency to bind O25b antigen and the specificity or selectivity to preferentially bind to the O25b antigen relative to other antigens of E. coli, e.g. binding to O25b and not binding to the O25a antigen of E. coli, or not significantly binding the O25a antigen, or cross-specifically binding both, O25b and O25a antigens, but not binding to other antigens of E. coli.

Functionally active variants may be obtained, e.g. by changing the sequence of a parent antibody, e.g. an antibody comprising the same binding site as any of the antibodies as listed in Table 1 and FIG. 2, but with modifications within an antibody region besides the binding site, or derived from such parent antibody by a modification within the binding site but that does not impair the antigen binding, and preferably would have substantially the same biological activity as the parent antibody or even an improved activity, including the ability to specifically or selectively bind O25b antigen, e.g. binding to O25b and not binding to the O25a antigen of E. coli, or not significantly binding the O25a antigen, or cross-specifically binding both, O25b and O25a antigens, but not binding to other antigens of E. coli. Optionally, the functionally active variants may further include a potency of complement mediated killing in an SBA assay, and/or optionally further include a potency of an antibody mediated phagocytosis in an OPK assay, and/or optionally further include endotoxin neutralization function in a LAL assay, e.g. with substantially the same biological activity, as determined by the specific binding assay or functional test to target (MDR) E. coli.

The term “substantially the same biological activity” as used herein refers to the activity as indicated by substantially the same activity being at least 20%, at least 50%, at least 75%, at least 90%, e.g. at least 100%, or at least 125%, or at least 150%, or at least 175%, or e.g. up to 200% of the activity as determined for the comparable or parent antibody.

The preferred variants or derivatives as described herein are functionally active with regard to the antigen binding, preferably which have a potency to specifically bind O25b antigen, and not binding to other antigens of E. coli, e.g. binding to O25b and not binding to the O25a antigen of E. coli, or not significantly binding the O25a antigen, or cross-specifically binding both, O25b and O25a antigens, e.g. preferentially binding the O25b antigen relative to O25a, or binding the O25b with higher affinity as compared to current polyclonal typing sera raised against O25 (O25a) strains. Preferred variants are not binding to other antigens of E. coli, with a Kd value difference of at least 2 logs, preferably at least 3 logs, and optionally further including a potency of complement mediated killing in an SBA assay, e.g. to achieve significant reduction in bacterial counts relative to control samples not containing the antibody, and/or optionally further including a potency of an antibody mediated phagocytosis in an OPK assay, such as to achieve significant reduction in bacterial counts relative to control samples not containing the antibody, and/or optionally further including endotoxin neutralization function in a LAL or TLR4 signaling assay, such as to achieve significant reduction in free LPS relative to control samples not containing the antibody, e.g. with substantially the same biological activity, as determined by the specific binding assay or functional test to target MDR E. coli. The significant reduction of analytes in the various assays typically means the reduction of at least 50%, preferably at least 60%, 70%, 80%, 90%, 95% or 98% up to complete reduction of about 100% (+/−1%).

In a preferred embodiment the functionally active variant of a parent antibody

a) is a biologically active fragment of the antibody, the fragment comprising at least 50% of the sequence of the molecule, preferably at least 60%, at least 70%, at least 80%, at least 90%, or at least 95% and most preferably at least 97%, 98% or 99%;

b) is derived from the antibody by at least one amino acid substitution, addition and/or deletion, wherein the functionally active variant has a sequence identity to the molecule or part of it, such as an antibody of at least 50% sequence identity, preferably at least 60%, more preferably at least 70%, more preferably at least 80%, still more preferably at least 90%, even more preferably at least 95% and most preferably at least 97%, 98% or 99%; and/or

c) consists of the antibody or a functionally active variant thereof and additionally at least one amino acid or nucleotide heterologous to the polypeptide or the nucleotide sequence.

In one preferred embodiment of the invention, the functionally active variant of the antibody according to the invention is essentially identical to the variant described above, but differs from its polypeptide or the nucleotide sequence, respectively, in that it is derived from a homologous sequence of a different species. These are referred to as naturally occurring variants or analogs.

The term “functionally active variant” also includes naturally occurring allelic variants, as well as mutants or any other non-naturally occurring variants. As is known in the art, an allelic variant is an alternate form of a (poly) peptide that is characterized as having a substitution, deletion, or addition of one or more amino acids that does essentially not alter the biological function of the polypeptide.

Functionally active variants may be obtained by sequence alterations in the polypeptide or the nucleotide sequence, e.g. by one or more point mutations, wherein the sequence alterations retains or improves a function of the unaltered polypeptide or the nucleotide sequence, when used in combination of the invention. Such sequence alterations can include, but are not limited to, (conservative) substitutions, additions, deletions, mutations and insertions.

Specific functionally active variants are CDR variants. A CDR variant includes an amino acid sequence modified by at least one amino acid in the CDR region, wherein said modification can be a chemical or a partial alteration of the amino acid sequence, which modification permits the variant to retain the biological characteristics of the unmodified sequence. A partial alteration of the CDR amino acid sequence may be by deletion or substitution of one to several amino acids, e.g. 1, 2, 3, 4 or 5 amino acids, or by addition or insertion of one to several amino acids, e.g. 1, 2, 3, 4 or 5 amino acids, or by a chemical derivatization of one to several amino acids, e.g. 1, 2, 3, 4 or 5 amino acids, or combination thereof. The substitutions in amino acid residues may be conservative substitutions, for example, substituting one hydrophobic amino acid for an alternative hydrophobic amino acid.

Conservative substitutions are those that take place within a family of amino acids that are related in their side chains and chemical properties. Examples of such families are amino acids with basic side chains, with acidic side chains, with non-polar aliphatic side chains, with non-polar aromatic side chains, with uncharged polar side chains, with small side chains, with large side chains etc.

A point mutation is particularly understood as the engineering of a polynucleotide that results in the expression of an amino acid sequence that differs from the non-engineered amino acid sequence in the substitution or exchange, deletion or insertion of one or more single (non-consecutive) or doublets of amino acids for different amino acids.

Preferred point mutations refer to the exchange of amino acids of the same polarity and/or charge. In this regard, amino acids refer to twenty naturally occurring amino acids encoded by sixty-four triplet codons. These 20 amino acids can be split into those that have neutral charges, positive charges, and negative charges:

The “neutral” amino acids are shown below along with their respective three-letter and single-letter code and polarity:

Alanine: (Ala, A) nonpolar, neutral;

Asparagine: (Asn, N) polar, neutral;

Cysteine: (Cys, C) nonpolar, neutral;

Glutamine: (Gln, Q) polar, neutral;

Glycine: (Gly, G) nonpolar, neutral;

Isoleucine: (Ile, I) nonpolar, neutral;

Leucine: (Leu, L) nonpolar, neutral;

Methionine: (Met, M) nonpolar, neutral;

Phenylalanine: (Phe, F) nonpolar, neutral;

Proline: (Pro, P) nonpolar, neutral;

Serine: (Ser, S) polar, neutral;

Threonine: (Thr, T) polar, neutral;

Tryptophan: (Trp, W) nonpolar, neutral;

Tyrosine: (Tyr, Y) polar, neutral;

Valine: (Val, V) nonpolar, neutral; and

Histidine: (His, H) polar, positive (10%) neutral (90%).

The “positively” charged amino acids are:

Arginine: (Arg, R) polar, positive; and

Lysine: (Lys, K) polar, positive.

The “negatively” charged amino acids are:

Aspartic acid: (Asp, D) polar, negative; and

Glutamic acid: (Glu, E) polar, negative.

“Percent (%) amino acid sequence identity” with respect to the antibody sequences and homologs described herein is defined as the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in the specific polypeptide sequence, after aligning the sequence and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. Those skilled in the art can determine appropriate parameters for measuring alignment, including any algorithms needed to achieve maximal alignment over the full length of the sequences being compared.

An antibody variant is specifically understood to include homologs, analogs, fragments, modifications or variants with a specific glycosylation pattern, e.g. produced by glycoengineering, which are functional and may serve as functional equivalents, e.g. binding to the specific targets and with functional properties.

An antibody of the present invention may or may not exhibit Fc effector function. Though the mode of action is mainly mediated by neutralizing antibodies without Fc effector functions, Fc can recruit complement and aid elimination of the target antigen, such as a toxin, from the circulation via formation of immune complexes.

Specific antibodies may be devoid of an active Fc moiety, thus, either composed of antibody domains that do not contain an Fc part of an antibody or that do not contain an Fcgamma receptor binding site, or comprising antibody domains lacking Fc effector function, e.g. by modifications to reduce Fc effector functions, in particular to abrogate or reduce ADCC and/or CDC activity. Alternative antibodies may be engineered to incorporate modifications to increase Fc effector functions, in particular to enhance ADCC and/or CDC activity.

Such modifications may be effected by mutagenesis, e.g. mutations in the Fcgamma receptor binding site or by derivatives or agents to interfere with ADCC and/or CDC activity of an antibody format, so to achieve reduction or increase of Fc effector function.

A significant reduction of Fc effector function is typically understood to refer to Fc effector function of less than 10% of the unmodified (wild-type) format, preferably less than 5%, as measured by ADCC and/or CDC activity. A significant increase of Fc effector function is typically understood to refer to an increase in Fc effector function of at least 10% of the unmodified (wild-type) format, preferably at least 20%, 30%, 40% or 50%, as measured by ADCC and/or CDC activity.

The term “glycoengineered” variants with respect to antibody sequences shall refer to glycosylation variants having modified immunogenic or immunomodulatory (e.g. anti-inflammatory) properties, ADCC and/or CDC, as a result of the glycoengineering. All antibodies contain carbohydrate structures at conserved positions in the heavy chain constant regions, with each isotype possessing a distinct array of N-linked carbohydrate structures, which variably affect protein assembly, secretion or functional activity. IgG1 type antibodies are glycoproteins that have a conserved N linked glycosylation site at Asn297 in each CH2 domain. The two complex bi-antennary oligosaccharides attached to Asn297 are buried between the CH2 domains, forming extensive contacts with the polypeptide backbone, and their presence is essential for the antibody to mediate effector functions such as antibody dependent cellular cytotoxicity (ADCC). Removal of N-Glycan at N297, e.g. through mutating N297, e.g. to A, or T299 typically results in aglycosylated antibody formats with reduced ADCC. Specifically, the antibody of the invention may be glycosylated or glycoengineered, or aglycosylated antibodies.

Major differences in antibody glycosylation occur between cell lines, and even minor differences are seen for a given cell line grown under different culture conditions. Expression in bacterial cells typically provides for an aglycosylated antibody. CHO cells with tetracycline-regulated expression of β(1,4)-N-acetylglucosaminyltransferase III (GnTIII), a glycosyltransferase catalyzing formation of bisecting GlcNAc, was reported to have improved ADCC activity (Umana et al., 1999, Nature Biotech. 17:176-180). In addition to the choice of host cells, factors that affect glycosylation during recombinant production of antibodies include growth mode, media formulation, culture density, oxygenation, pH, purification schemes and the like.

The term “antigen-binding site” or “binding site” refers to the part of an antibody that participates in antigen binding. The antigen binding site is formed by amino acid residues of the N-terminal variable (“V”) regions of the heavy (“H”) and/or light (“L”) chains, or the variable domains thereof. Three highly divergent stretches within the V regions of the heavy and light chains, referred to as “hypervariable regions”, are interposed between more conserved flanking stretches known as framework regions, The antigen-binding site provides for a surface that is complementary to the three-dimensional surface of a bound epitope or antigen, and the hypervariable regions are referred to as “complementarity-determining regions”, or “CDRs.” The binding site incorporated in the CDRs is herein also called “CDR binding site”.

The term “antigen” as used herein interchangeably with the terms “target” or “target antigen” shall refer to a whole target molecule or a fragment of such molecule recognized by an antibody binding site. Specifically, substructures of an antigen, e.g. a polypeptide or carbohydrate structure, generally referred to as “epitopes”, e.g. B-cell epitopes or T-cell epitope, which are immunologically relevant, may be recognized by such binding site. Specific antigens like the O25b or O25a antigens are provided as isolated antigens, or else in the form of E. coli cells or cell fractions.

The term “epitope” as used herein shall in particular refer to a molecular structure which may completely make up a specific binding partner or be part of a specific binding partner to a binding site of an antibody. An epitope may either be composed of a carbohydrate, a peptidic structure, a fatty acid, an organic, biochemical or inorganic substance or derivatives thereof and any combinations thereof. If an epitope is comprised in a peptidic structure, such as a peptide, a polypeptide or a protein, it will usually include at least 3 amino acids, preferably 5 to 40 amino acids, and more preferably between about 10-20 amino acids. Epitopes can be either linear or conformational epitopes. A linear epitope is comprised of a single segment of a primary sequence of a polypeptide or carbohydrate chain. Linear epitopes can be contiguous or overlapping.

Conformational epitopes are comprised of amino acids or carbohydrates brought together by folding the polypeptide to form a tertiary structure and the amino acids are not necessarily adjacent to one another in the linear sequence. Specifically and with regard to polypeptide antigens a conformational or discontinuous epitope is characterized by the presence of two or more discrete amino acid residues, separated in the primary sequence, but assembling to a consistent structure on the surface of the molecule when the polypeptide folds into the native protein/antigen.

Herein the term “epitope” shall particularly refer to the single epitope recognized by an antibody, or the mixture of epitopes comprising epitope variants, each recognized by a cross-reactive antibody.

The term “expression” is understood in the following way. Nucleic acid molecules containing a desired coding sequence of an expression product such as e.g. an antibody as described herein, and control sequences such as e.g. a promoter in operable linkage, may be used for expression purposes. Hosts transformed or transfected with these sequences are capable of producing the encoded proteins. In order to effect transformation, the expression system may be included in a vector; however, the relevant DNA may also be integrated into the host chromosome. Specifically the term refers to a host cell and compatible vector under suitable conditions, e.g. for the expression of a protein coded for by foreign DNA carried by the vector and introduced to the host cell.

Coding DNA is a DNA sequence that encodes a particular amino acid sequence for a particular polypeptide or protein such as e.g. an antibody. Promoter DNA is a DNA sequence which initiates, regulates, or otherwise mediates or controls the expression of the coding DNA. Promoter DNA and coding DNA may be from the same gene or from different genes, and may be from the same or different organisms. Recombinant cloning vectors will often include one or more replication systems for cloning or expression, one or more markers for selection in the host, e.g. antibiotic resistance, and one or more expression cassettes.

“Vectors” used herein are defined as DNA sequences that are required for the transcription of cloned recombinant nucleotide sequences, i.e. of recombinant genes and the translation of their mRNA in a suitable host organism.

An “expression cassette” refers to a DNA coding sequence or segment of DNA that code for an expression product that can be inserted into a vector at defined restriction sites. The cassette restriction sites are designed to ensure insertion of the cassette in the proper reading frame. Generally, foreign DNA is inserted at one or more restriction sites of the vector DNA, and then is carried by the vector into a host cell along with the transmissible vector DNA. A segment or sequence of DNA having inserted or added DNA, such as an expression vector, can also be called a “DNA construct”.

Expression vectors comprise the expression cassette and additionally usually comprise an origin for autonomous replication in the host cells or a genome integration site, one or more selectable markers (e.g. an amino acid synthesis gene or a gene conferring resistance to antibiotics such as zeocin, kanamycin, G418 or hygromycin), a number of restriction enzyme cleavage sites, a suitable promoter sequence and a transcription terminator, which components are operably linked together. The term “vector” as used herein includes autonomously replicating nucleotide sequences as well as genome integrating nucleotide sequences. A common type of vector is a “plasmid”, which generally is a self-contained molecule of double-stranded DNA that can readily accept additional (foreign) DNA and which can readily be introduced into a suitable host cell. A plasmid vector often contains coding DNA and promoter DNA and has one or more restriction sites suitable for inserting foreign DNA. Specifically, the term “vector” or “plasmid” refers to a vehicle by which a DNA or RNA sequence (e.g. a foreign gene) can be introduced into a host cell, so as to transform the host and promote expression (e.g. transcription and translation) of the introduced sequence.

The term “host cell” as used herein shall refer to primary subject cells transformed to produce a particular recombinant protein, such as an antibody as described herein, and any progeny thereof. It should be understood that not all progeny are exactly identical to the parental cell (due to deliberate or inadvertent mutations or differences in environment), however, such altered progeny are included in these terms, so long as the progeny retain the same functionality as that of the originally transformed cell. The term “host cell line” refers to a cell line of host cells as used for expressing a recombinant gene to produce recombinant polypeptides such as recombinant antibodies. The term “cell line” as used herein refers to an established clone of a particular cell type that has acquired the ability to proliferate over a prolonged period of time. Such host cell or host cell line may be maintained in cell culture and/or cultivated to produce a recombinant polypeptide.

The term “isolated” or “isolation” as used herein with respect to a nucleic acid, an antibody or other compound shall refer to such compound that has been sufficiently separated from the environment with which it would naturally be associated, so as to exist in “substantially pure” form. “Isolated” does not necessarily mean the exclusion of artificial or synthetic mixtures with other compounds or materials, or the presence of impurities that do not interfere with the fundamental activity, and that may be present, for example, due to incomplete purification. In particular, isolated nucleic acid molecules of the present invention are also meant to include those which are not naturally occurring, e.g. codon-optimized nucleic acids or cDNA, or chemically synthesized.

Likewise, the isolated antibody of the invention is specifically non-naturally occurring, e.g. as provided in a combination preparation with another antibody or active agent, which combination does not occur in nature, or an optimized or affinity-maturated variant of a naturally occurring antibody, or an antibody with a framework-region which is engineered to improve the manufacturability of the antibody.

With reference to nucleic acids of the invention, the term “isolated nucleic acid” is sometimes used. This term, when applied to DNA, refers to a DNA molecule that is separated from sequences with which it is immediately contiguous in the naturally occurring genome of the organism in which it originated. For example, an “isolated nucleic acid” may comprise a DNA molecule inserted into a vector, such as a plasmid or virus vector, or integrated into the genomic DNA of a prokaryotic or eukaryotic cell or host organism. When applied to RNA, the term “isolated nucleic acid” refers primarily to an RNA molecule encoded by an isolated DNA molecule as defined above. Alternatively, the term may refer to an RNA molecule that has been sufficiently separated from other nucleic acids with which it would be associated in its natural state (i.e., in cells or tissues). An “isolated nucleic acid” (either DNA or RNA) may further represent a molecule produced directly by biological or synthetic means and separated from other components present during its production.

With reference to polypeptides or proteins, such as isolated antibodies or epitopes of the invention, the term “isolated” shall specifically refer to compounds that are free or substantially free of material with which they are naturally associated such as other compounds with which they are found in their natural environment, or the environment in which they are prepared (e g. cell culture) when such preparation is by recombinant DNA technology practiced in vitro or in vivo. Isolated compounds can be formulated with diluents or adjuvants and still for practical purposes be isolated—for example, the polypeptides or polynucleotides can be mixed with pharmaceutically acceptable carriers or excipients when used in diagnosis or therapy. In particular, the isolated antibody of the invention differs from polyclonal serum preparations raised against O25(a) strains, because it is provided in the isolated and purified form, preferably provided in a preparation comprising the isolated antibody as the only active substance. This does not preclude, however, that the isolated antibody is provided in a combination product comprising a limited number of further well-defined (isolated) antibodies. Isolated antibodies may as well be provided on a solid, semi-liquid or liquid carrier, such as beads.

The term “neutralizing” or “neutralization” is used herein in the broadest sense and refers to any molecule that inhibits a pathogen, such as MDR E. coli from infecting a subject, or to inhibit the pathogen from promoting infections by producing potent protein toxins, or to inhibit the toxins from damaging a target cell in a subject, irrespective of the mechanism by which neutralization is achieved. Neutralization can be achieved, e.g., by an antibody that inhibits the binding and/or interaction of the MDR E. coli endotoxin with its cognate receptor on target cells (e.g. binding to the TLR4 receptor). Neutralization can further occur by removal of endotoxin molecules from the circulation by Fc mediated functions.

The neutralization potency is typically determined in a standard assay, e.g. LAL test, where the inhibition of endotoxin's biological activity is measured, e.g. by colorimetry.

The term “MDR E. coli” is understood in the following way: Infections with multi-drug resistant E. coli that are in a significant portion due to the ST131-O25b:H4 clonal lineage, which emerged only in the last decade and became a globally spread dominant resistant clone. Multi-resistant E. coli is particularly understood as those strains demonstrating resistance to three or more classes of antibiotics, e.g. the following agents/groups: penicillins, cephalosporins, carbapenems, aminoglycosides, tetracyclines, fuoroquinolones, nitrofurantoin, trimethoprim (and its combinations), fosfomycin, polymixins, chloramphenicol, azthreonam, tigecycline.

The acidic capsular polysaccharide (CPS) is a thick, mucous-like, layer of polysaccharide that surrounds most pathogen E. coli. It is, thus, surprising that the specific epitope recognized by an antibody of the invention would specifically be accessible on both, the encapsulated and the non-encapsulated MDR E. coli strain.

Antibodies combating or neutralizing MDR E. coli are interfering with the pathogens and pathogenic reactions, thus able to limit or prevent infection and/or to ameliorate a disease condition resulting from such infection, or to inhibit MDR E. coli pathogenesis, in particular dissemination and replication into or within sterile body compartments/sites of the host. In this regard “protective antibodies” are understood herein as antibodies that are responsible for immunity to an infectious agent observed in active or passive immunity. In particular, protective antibodies as described herein are possibly used for therapeutic purposes, e.g. for prophylaxis or therapy, to prevent, ameliorate, treat or at least partially arrest disease symptoms, side effects or progression of disease induced by a pathogen. Specifically, protective antibodies are able to kill or impede replication of live E. coli cells by e.g. inducing serum bactericidal or opsonophagocytic activities, or remove whole bacterial cells or the LPS molecules thereof from the sterile body sites following therapeutic applications (i.e. given on an established infection). Alternatively, prophylactically applied protective antibodies inhibit establishment of an infection (i.e. spread of E. coli from non-sterile sites to sterile body compartments) by one of the abovementioned or other mechanisms.

The term “O25b antigen” is herein understood as the LPS O-antigen with structure elucidated in FIG. 8 (a). The structure is similar, but distinct from that of the O25a antigen. O25b is herein understood as a serotype, which is similar, but distinct from O25a.

The term “O25a antigen” is herein understood as the antigen made of the pentasaccharide repeating unit described by Kenne et al. Before identifying the O25b antigen, the term O25 has stood for O25a as described herein (see FIG. 8 (b)).

The term “recombinant” as used herein shall mean “being prepared by or the result of genetic engineering”. A recombinant host specifically comprises an expression vector or cloning vector, or it has been genetically engineered to contain a recombinant nucleic acid sequence, in particular employing nucleotide sequence foreign to the host. A recombinant protein is produced by expressing a respective recombinant nucleic acid in a host. The term “recombinant antibody”, as used herein, includes antibodies that are prepared, expressed, created or isolated by recombinant means, such as (a) antibodies isolated from an animal (e.g., a mouse) that is transgenic or transchromosomal for human immunoglobulin genes or a hybridoma prepared therefrom, (b) antibodies isolated from a host cell transformed to express the antibody, e.g., from a transfectoma, (c) antibodies isolated from a recombinant, combinatorial human antibody library, and (d) antibodies prepared, expressed, created or isolated by any other means that involve splicing of human immunoglobulin gene sequences to other DNA sequences. Such recombinant antibodies comprise antibodies engineered to include rearrangements and mutations which occur, for example, during antibody maturation.

As used herein, the term “specificity” or “specific binding” refers to a binding reaction which is determinative of the cognate ligand of interest in a heterogeneous population of molecules. Thus, under designated conditions (e.g. immunoassay conditions), an antibody specifically binds to its particular target and does not bind in a significant amount to other molecules present in a sample. The specific binding means that binding is selective in terms of target identity, high, medium or low binding affinity or avidity, as selected. Selective binding is usually achieved if the binding constant or binding dynamics is at least 10 fold different (understood as at least 1 log difference), preferably the difference is at least 100 fold (understood as at least 2 logs difference), and more preferred a least 1000 fold (understood as at least 3 logs difference) as compared to another antigen.

As used herein, the term “specificity” or “specific binding” refers to a binding reaction which is determinative of the cognate ligand of interest in a heterogeneous population of molecules. Thus, under designated conditions (e.g. immunoassay conditions), an antibody specifically binds to its particular target and does not bind in a significant amount to other molecules present in a sample. The specific binding means that binding is selective in terms of target identity, high, medium or low binding affinity or avidity, as selected. Selective binding is usually achieved if the binding constant or binding dynamics is at least 10 fold different (understood as at least 1 log difference), preferably the difference is at least 100 fold (understood as at least 2 logs difference), and more preferred a least 1000 fold (understood as at least 3 logs difference). The term “specificity” or “specific binding” is also understood to apply to binders which bind to one or more molecules, e.g. cross-specific binders.

The antibody of the invention specifically is selective in only binding the O25b antigen, or preferentially binding the O25b antigen relative to the O25a antigen, or binding the O25b with higher affinity as compared to polyclonal serum raised against O25a strains, which serum binds to the O25b antigen with a low affinity. Thus, the antibody of the invention may be understood to differentially bind those antigens, e.g. at least with equal affinity, or more than equal affinity, such as with a different affinity with a Kd difference of at least 1 log, preferably at least 2 logs, more preferably at least 3 logs. Such antibody selectively binding to the O25b antigen relative to the O25a antigen is preferably used for diagnostic or therapeutic purposes. For some diagnostic purposes an antibody is specifically used which only binds the O25b antigen in a detectable manner.

The differential binding affinity to preferably bind the O25b antigen relative to other E. coli antigens, e.g. any carbohydrate antigens other than O25 antigen or any core antigens, is preferably at least 10-fold higher, i.e. with a Kd difference of at least 10, preferably at least 100-fold higher, more preferred at least 1000 fold higher.

The differential binding affinity to preferentially bind the O25b antigen is specifically at least 5 fold, or at least 6-fold, or at least 7-fold, or at least 8-fold, or at least 9-fold, or at least 10-fold higher, in comparison to commercial typing serum, such as the high titer E. coli O25 antiserum from Statens Serum Institut (#81369).

The differential binding affinity to preferentially bind the O25b antigen relative to the O25a antigen is specifically at least equal or more than equal, e.g. at least 1.5 fold, or at least 2-fold, or at least 3-fold, or at least 4-fold, or at least 5 fold, or at least 6-fold, or at least 7-fold, or at least 8-fold, or at least 9-fold, or at least 10-fold higher.

Preferred antibodies of the invention are binding any of said individual antigens, in particular the O25b antigen, with a high affinity, in particular with a high on and/or a low off rate, or a high avidity of binding. The binding affinity of an antibody is usually characterized in terms of the concentration of the antibody, at which half of the antigen binding sites are occupied, known as the dissociation constant (Kd, or K_(D)). Usually a binder is considered a high affinity binder with a Kd<10⁻⁷ M, in some cases, e.g. for therapeutic purposes with higher affinities, e.g. with a Kd<10⁻⁸ M, preferably a Kd<10⁻⁹ M, even more preferred is a Kd<10⁻¹⁰ M.

Yet, in a particularly preferred embodiment the individual antigen binding affinities are of medium affinity, e.g. with a Kd of less than 10⁻⁶ and up to 10⁻⁸ M, e.g. when binding to at least two antigens.

Medium affinity binders may be provided according to the invention, preferably in conjunction with an affinity maturation process, if necessary.

Affinity maturation is the process by which antibodies with increased affinity for a target antigen are produced. Any one or more methods of preparing and/or using affinity maturation libraries available in the art may be employed in order to generate affinity matured antibodies in accordance with various embodiments of the invention disclosed herein. Exemplary such affinity maturation methods and uses, such as random mutagenesis, bacterial mutator strains passaging, site-directed mutagenesis, mutational hotspots targeting, parsimonious mutagenesis, antibody shuffling, light chain shuffling, heavy chain shuffling, CDR1 and/or CDR1 mutagenesis, and methods of producing and using affinity maturation libraries amenable to implementing methods and uses in accordance with various embodiments of the invention disclosed herein, include, for example, those disclosed in: Prassler et al. (2009); Immunotherapy, Vol. 1(4), pp. 571-583; Sheedy et al. (2007), Biotechnol. Adv., Vol. 25(4), pp. 333-352; WO2012/009568; WO2009/036379; WO2010/105256; US2002/0177170; WO2003/074679.

With structural changes of an antibody, including amino acid mutagenesis or as a consequence of somatic mutation in immunoglobulin gene segments, variants of a binding site to an antigen are produced and selected for greater affinities. Affinity matured antibodies may exhibit a several logfold greater affinity than a parent antibody. Single parent antibodies may be subject to affinity maturation. Alternatively pools of antibodies with similar binding affinity to the target antigen may be considered as parent structures that are varied to obtain affinity matured single antibodies or affinity matured pools of such antibodies.

The preferred affinity maturated variant of an antibody according to the invention exhibits at least a 2 fold increase in affinity of binding, preferably at least a 5, preferably at least 10, preferably at least 50, or preferably at least 100 fold increase. The affinity maturation may be employed in the course of the selection campaigns employing respective libraries of parent molecules, either with antibodies having medium binding affinity to obtain the antibody of the invention having the specific target binding property of a binding affinity Kd<10⁻⁸ M. Alternatively, the affinity may be even more increased by affinity maturation of the antibody according to the invention to obtain the high values corresponding to a Kd of less than 10⁻⁹ M, preferably less than 10⁻¹⁰ M or even less than 10⁻¹¹ M, most preferred in the picomolar range.

In certain embodiments binding affinity is determined by an affinity ELISA assay. In certain embodiments binding affinity is determined by a BIAcore, ForteBio or MSD assays. In certain embodiments binding affinity is determined by a kinetic method. In certain embodiments binding affinity is determined by an equilibrium/solution method.

Use of the term “having the same specificity”, “having the same binding site” or “binding the same epitope” indicates that equivalent monoclonal antibodies exhibit the same or essentially the same, i.e. similar immunoreaction (binding) characteristics and compete for binding to a pre-selected target binding sequence. The relative specificity of an antibody molecule for a particular target can be relatively determined by competition assays, e.g. as described in Harlow, et al., ANTIBODIES: A LABORATORY MANUAL, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1988).

The term “subject” as used herein shall refer to a warm-blooded mammalian, particularly a human being. In particular the medical use of the invention or the respective method of treatment applies to a subject in need of prophylaxis or treatment of a disease condition associated with a MDR E. coli infection or suffering from disease, including early stage or late stage disease. The term “patient” includes human and other mammalian subjects that receive either prophylactic or therapeutic treatment. The term “treatment” is thus meant to include both prophylactic and therapeutic treatment.

A subject is e.g. treated for prophylaxis or therapy of MDR E. coli disease conditions. In particular, the subject is treated, which is either at risk of infection or developing such disease or disease recurrence, or a subject that is suffering from such infection and/or disease associated with such infection.

Specifically, the method for treating, preventing, or delaying a disease condition in a subject as described herein, is by interfering with the pathogenesis of MDR E. coli as causal agent of the condition.

Specifically the term “prophylaxis” refers to preventive measures which is intended to encompass prevention of the onset of pathogenesis or prophylactic measures to reduce the risk of pathogenesis.

For example, the antibody of the present invention may be used prophylactically to inhibit onset of MDR E. coli infection, or therapeutically to treat MDR E. coli infection, particularly MDR E. coli infections that are known to be refractory or in the case of the specific subject, have proven refractory to treatment with other conventional antibiotic therapy.

The term “substantially pure” or “purified” as used herein shall refer to a preparation comprising at least 50% (w/w), preferably at least 60%, 70%, 80%, 90% or 95% of a compound, such as a nucleic acid molecule or an antibody. Purity is measured by methods appropriate for the compound (e.g. chromatographic methods, polyacrylamide gel electrophoresis, HPLC analysis, and the like).

The term “therapeutically effective amount”, used herein interchangeably with any of the terms “effective amount” or “sufficient amount” of a compound, e.g. an antibody of the present invention, is a quantity or activity sufficient to, when administered to the subject effect beneficial or desired results, including clinical results, and, as such, an effective amount or synonym thereof depends upon the context in which it is being applied.

An effective amount is intended to mean that amount of a compound that is sufficient to treat, prevent or inhibit such diseases or disorder. In the context of disease, therapeutically effective amounts of the antibody as described herein are specifically used to treat, modulate, attenuate, reverse, or affect a disease or condition that benefits from an inhibition of (MDR) E. coli pathogenesis, for example, adhesion and colonization of mucosal surfaces, uncontrolled replication within sterile body sites, and toxicity of host cells by bacterial products.

The amount of the compound that will correspond to such an effective amount will vary depending on various factors, such as the given drug or compound, the pharmaceutical formulation, the route of administration, the type of disease or disorder, the identity of the subject or host being treated, and the like, but can nevertheless be routinely determined by one skilled in the art.

A therapeutically effective amount of the antibody as described herein, such as provided to a human patient in need thereof, may specifically be in the range of 0.5-50 mg/kg, preferably 5-40 mg/kg, even more preferred up to 20 mg/kg, up to 10 mg/kg, up to 5 mg/kg, though higher doses may be indicated e.g. for treating acute disease conditions.

Moreover, a treatment or prevention regime of a subject with a therapeutically effective amount of the antibody of the present invention may consist of a single administration, or alternatively comprise a series of applications. For example, the antibody may be administered at least once a year, at least once a half-year or at least once a month. However, in another embodiment, the antibody may be administered to the subject from about one time per week to about a daily administration for a given treatment. The length of the treatment period depends on a variety of factors, such as the severity of the disease, either acute or chronic disease, the age of the patient, the concentration and the activity of the antibody format. It will also be appreciated that the effective dosage used for the treatment or prophylaxis may increase or decrease over the course of a particular treatment or prophylaxis regime. Changes in dosage may result and become apparent by standard diagnostic assays known in the art. In some instances, chronic administration may be required.

According to a specific aspect, the invention provides for exemplary antibodies as detailed in the figures provided herein, and further antibody variants, in particular including variants binding to essentially the same epitope, as the parent antibody which is characterized by the specific binding site formed by the VH and the VL amino acid sequences, or else by the HC and the LC amino acid sequences of FIG. 2, or the binding sites formed by such VH/VL domains. Such antibodies may e.g. be functionally active variant antibodies obtained by modifying the respective CDR or antibody sequence of the parent antibody. It is well understood that any antibody sequence as described herein is considered a “parent” sequence which is subject to variation, e.g. by point mutations.

Exemplary parent antibodies are described in the examples section below and in FIGS. 1 and 2. The antibodies of FIG. 2 are variant antibodies derived from parent antibodies of Table 1, namely antibodies designated 2A7, 8A1, 4D5 and 3E9 and the respective variants with different HC/LC combinations, and which are obtained by humanization and optionally affinity maturation. These variant antibodies bind to the target antigen, thus, are considered functionally active. It is feasible that also variant VH or VL domains or variant HC or LC chains, e.g. with modifications in the respective FR or CDR sequences may be used, which are functionally active, e.g. binding to the same epitope or comprising the same binding site or having the same binding characteristics as the parent antibody. It is also feasible that some of the FR or CDR sequences of the antibodies described herein may be exchanged by those of other antibodies, e.g. of antibodies as listed in FIG. 1 or 2.

Antibodies are said to “bind to the same epitope” or “comprising the same binding site” or have “essentially the same binding” characteristics, if the antibodies cross-compete so that only one antibody can bind to the epitope at a given point of time, i.e. one antibody prevents the binding or modulating effect of the other.

The term “compete” or “cross-compete”, as used herein with regard to an antibody, means that a first antibody, or an antigen-binding portion thereof, binds to an epitope in a manner sufficiently similar to the binding of a second antibody, or an antigen-binding portion thereof, such that the result of binding of the first antibody with its cognate epitope is detectably decreased in the presence of the second antibody compared to the binding of the first antibody in the absence of the second antibody. The alternative, where the binding of the second antibody to its epitope is also detectably decreased in the presence of the first antibody, can, but need not be the case. That is, a first antibody can inhibit the binding of a second antibody to its epitope without that second antibody inhibiting the binding of the first antibody to its respective epitope. However, where each antibody detectably inhibits the binding of the other antibody with its cognate epitope, whether to the same, greater, or lesser extent, the antibodies are said to “cross-compete” with each other for binding of their respective epitope(s). Both competing and cross-competing antibodies are encompassed by the present invention.

Competition herein means a greater relative inhibition than about 30% as determined by competition ELISA analysis or by ForteBio analysis. It may be desirable to set a higher threshold of relative inhibition as criteria of what is a suitable level of competition in a particular context, e.g., where the competition analysis is used to select or screen for new antibodies designed with the intended function of the binding of the antigen. Thus, for example, it is possible to set criteria for the competitive binding, wherein at least 40% relative inhibition is detected, or at least 50%, at least 60%, at least 70%, at least 80%, at least 90% or even at least 100%, before an antibody is considered sufficiently competitive.

As described herein, in one aspect the invention provides antibody molecules characterized by, e.g. the ability to compete with any of the antibodies listed in FIG. 1 or 2, for binding the O25b antigen.

Monoclonal antibodies (mAbs) highly specific to O25b have great potential as diagnostic reagents for the identification of MDR strains belonging to the ST131 lineage. Furthermore, in particular following humanization, these mAbs are suitable to be used for the prophylaxis (e.g. for high risk groups) and treatment of E. coli infections caused by ST131-O25b:H4 strains.

The O25b and O25a carbohydrate antigens were thought to be identical or very similar based on the fact that immune serum against O25 is routinely used in the diagnostic identification of E. coli strains expressing O25b antigens. The genetic background of O-antigen synthesis in ST131 strains was not fully elucidated, however, a specific gene within the rfb cluster (encoding O-antigen synthesis) forms the basis of PCR based identification of O25b strains. Furthermore, no structural data supported any difference between O25a and O25b antigens so far.

It was, thus, surprising that an antibody of invention could specifically bind the O25b antigen.

In order to confirm the genetic difference between O25b and O25a antigen expressing E. coli strains, the rfb cluster encoding O-antigen synthesis was sequenced from a clinical isolate of ST131-O25b:H4 strain 81009 (Szijarto et al, FEMS Microbiol Lett, 2012, 332:131-6) using a primer walk method starting with oligonucleotides specific to conserved flanking genes: gnd and galF. The resulting contig of the rfb operon is 11,300 bp long and only partially homologous to that encoding the O25 antigen synthesis enzymes (NCBI accession number GU014554). It turned out that a 2043 bp long segment at the 3′ end of the O25b rfb operon is non-homologous to the corresponding region of the O25 rfb operon, where this segment is replaced by a 6267 bp long sequence encoding fucose synthesis and transport.

The structure of the O-specific PS biological repeating unit (RU) present in LPS isolated from E. coli ST131 was analysed in details in a purified fraction built up by the core OS substituting with one repeating unit (RU). The RU of the LPS ST131 is an O-acetylated pentasaccharide with the structure depicted on FIG. 8 (a).

In fact, the RU structure of the ST131 O-PS differs from the LPS O25 RU reported by Kenne et al. (FIG. 8 (b)) and to the best of our knowledge it is a new O-serotype among E. coli lipopolysaccharides (Stenutz et al. FEMS Microbiol Rev. 2006 May; 30(3):382-403. Review). Additionally, preliminary results of MALDI-TOF mass spectrometry and composition analyses (sugar and methylation analyses) of a core oligosaccharide isolated from LPS ST131 supported K-12 type, what was previously reported by Szijártó V. et al. on the basis of genetic analyses (Szijarto et al, FEMS Microbiol Lett, 2012, 332:131-6). It was shown that LPS ST131 is consisted of two main core oligosaccharides (OS) glycoforms. The type of glycoform is dependent on the presence or absence of the O-specific polysaccharide (PS). Prevailing glycoform of the unsubstituted core OS is truncated version of K-12 core oligosaccharide, which is devoid of →7)-α-Hepp-(1→6)-α-Glcp disaccharide. Presence of that disaccharide is the difference between O-PS substituted core OS and nonsubstituted core OS.

A specific aspect refers to an antibody of the invention characterized by a specific anti-bacterial functional activity, such as complement mediated bacterial killing and opsonophagocytic uptake and killing.

According to a specific embodiment, the antibody of the invention has a cytotoxic activity in the presence of immune-effector cells as measured in a standard SBA or OPK assay. A cytotoxic activity as determined by either of an SBA or OPK assay may be shown for an antibody of the invention, if there is a significant increase in the percentage of bacterial killing as compared to a control. The bactericidal activity related to SBA or OPK is preferably measured as the absolute percentage increase, which is preferably higher than 5%, more preferably higher than 10%, even more preferred higher than 20%, 30%, 40% or 50%.

Phagocytic effector cells may be activated through another route employing activation of complement. Antibodies that bind to surface antigens on microorganisms attract the first component of the complement cascade with their Fc region and initiate activation of the “classical” complement system. These results in the stimulation of phagocytic effector cells, which ultimately kill the target by complement dependent cytotoxicity (CDC).

According to a specific embodiment, the antibody of the invention has a cytotoxic activity in the presence of immune-effector cells as measured in a standard ADCC or CDC assay. A cytotoxic activity as determined by either of an ADCC or CDC assay may be shown for an antibody of the invention, if there is a significant increase in the percentage of cytolysis as compared to a control. The cytotoxic activity related to ADCC or CDC is preferably measured as the absolute percentage increase, which is preferably higher than 5%, more preferably higher than 10%, even more preferred higher than 20%. Complement fixation might be specifically relevant, this mechanism can eliminate toxins from the infection site or blood by removal of the immune complexes formed.

According to a specific embodiment, the antibody of the invention has an immunomodulatory function exerted by the Fc part of IgGs. Altered glycosylation increasing the sialylation content, e.g. on the terminal galactose residues, possibly have an anti-inflammatory effect via DC-SIGN signaling. Preferential binding to Fcgamma receptor IIb (inhibitory) over the Ia, IIa and III Fcgamma receptors possibly provides an anti-inflammatory effect.

Antibodies of the present invention may be identified or obtained employing a hybridoma method. In such method, a mouse or other appropriate host animal, such as a hamster, is immunized to elicit lymphocytes that produce or are capable of producing antibodies that will specifically bind to the protein used for immunization. Alternatively, lymphocytes may be immunized in vitro. Lymphocytes then are fused with myeloma cells using a suitable fusing agent, such as polyethylene glycol, to form a hybridoma cell.

Culture medium in which hybridoma cells are growing is assayed for production of monoclonal antibodies directed against the antigen. Preferably, the binding specificity of monoclonal antibodies produced by hybridoma cells is determined by immunoprecipitation or by an in vitro binding assay, such as radioimmunoassay (RIA) or enzyme-linked immunoabsorbent assay (ELISA).

For example, the antibodies of the present invention may be obtained from source (parent) antibodies, e.g. obtained by immunizing mice with a non-encapsulated mutant of a representative ST131-O25b:H4 strain 81009 (e.g. 81009Δkps::kan) by replacing the kps cluster (encoding capsular synthesis) with a cassette encoding kanamycin resistance. Serum samples obtained from the mice may then be analyzed, and the spleen of the mouse showing the highest IgG titer against O25b antigen (in ELISA and Western Blot) may be used for hybridoma generation. Following sub-cloning, hybridoma clones may be selected, which secreted antibodies specific to O25b antigens as well as bound to the surface of live wild-type E. coli strains expressing O25b antigens. These mAbs may then be purified from hybridoma supernatants for further testing for its specific binding of O25b antigen and possibly for its differential binding affinity to preferentially bind O25b antigen relative to O25a antigen, and engineering of antibodies, e.g. for different diagnostic or therapeutic purposes.

Differentially binding antibodies, herein also called selective antibodies, in some instances, emerge through screening against single antigens. To increase the likelihood of isolating differentially binding clones one would apply multiple selective pressures by processively screening against the different antigens. Special mAb selection strategies employ the O25b and O25a components or other E. coli antigens in an alternating fashion.

Screening methods for identifying antibodies with the desired selective binding properties may be done by display technologies (using phage, bacterial, yeast or mammalian cells). Reactivity can be assessed based on ELISA, Western blotting or surface staining with flow cytometry, e.g. using standard assays.

Recombinant antigen(s) may e.g. be used for selecting antibodies from an antibody library, e.g. a yeast-displayed antibody library.

For example, the invention specifically provides for O25b specific antibodies, which are obtained by a process to identify antibodies with specificities to bind the O25b antigen, e.g. by a specific discovery selection scheme. Accordingly, an antibody library including antibodies showing reactivity with the O25b target, may be selected for reactivity with the target.

The invention further specifically provides for cross-specific antibodies, which are obtained by a process to identify antibodies with specificities to bind two targets, e.g. the O25b and O25a antigens, such as by a cross-reactive discovery selection scheme. Accordingly, an antibody library including antibodies showing reactivity with two targets, targets A and B, may first be selected for reactivity with one of the targets, e.g. target A, followed by selection for reactivity with the other target, e.g. target B. Each successive selection round reinforces the reactive strength of the resulting pool towards both targets. Accordingly, this method is particularly useful for identifying antibodies with cross-reactivity directed to the two different targets, and the potential to cross-neutralize a pathogen. The method can be extended to identifying antibodies showing reactivity towards further targets, by including additional rounds of enrichment towards the additional target(s).

In either event, selective binding can be further improved by antibody optimization methods known in the art. For example, certain regions of the variable regions of the immunoglobulin chains described herein may be subjected to one or more optimization strategies, including light chain shuffling, destinational mutagenesis, CDR amalgamation, and directed mutagenesis of selected CDR and/or framework regions.

Once differentially binding antibodies with the desired properties have been identified, the dominant epitope or epitopes recognized by the antibodies may be determined. Methods for epitope mapping are well-known in the art and are disclosed, for example, in Epitope Mapping: A Practical Approach, Westwood and Hay, eds., Oxford University Press, 2001.

Epitope mapping concerns the identification of the epitope to which an antibody binds. There are many methods known to those of skill in the art for determining the location of epitopes on proteins or formed by carbohydrates, including crystallography analysis of the antibody-antigen complex, competition assays, gene fragment expression assays, and synthetic peptide-based assays. An antibody that “binds the same epitope” as a reference antibody is herein understood in the following way. When two antibodies recognize epitopes that are identical or sterically overlapping epitopes, the antibodies are referred to as binding the same or essentially the same or substantially the same epitopes. A commonly used method for determining whether two antibodies bind to identical or sterically overlapping epitopes is the competition assay, which can be configured in all number of different formats, using either labeled antigen or labeled antibody. Usually, an antigen is immobilized on a 96-well plate, and the ability of unlabeled antibodies to block the binding of labeled antibodies is measured using radioactive or enzyme labels.

Once antibodies with the desired binding properties are identified, such antibodies, including antibody fragments can be produced by methods well-known in the art, including, for example, hybridoma techniques or recombinant DNA technology.

Recombinant monoclonal antibodies can, for example, be produced by isolating the DNA encoding the required antibody chains and transfecting a recombinant host cell with the coding sequences for expression, using well known recombinant expression vectors, e.g. the plasmids of the invention or expression cassette(s) comprising the nucleotide sequences encoding the antibody sequences. Recombinant host cells can be prokaryotic and eukaryotic cells, such as those described above.

According to a specific aspect, the nucleotide sequence may be used for genetic manipulation to humanize the antibody or to improve the affinity, or other characteristics of the antibody. For example, the constant region may be engineered to more nearly resemble human constant regions to avoid immune response, if the antibody is used in clinical trials and treatments in humans. It may be desirable to genetically manipulate the antibody sequence to obtain greater affinity to the target O25b and greater efficacy against MDR E. coli. It will be apparent to one of skill in the art that one or more polynucleotide changes can be made to the antibody and still maintain its binding ability to the target O25b.

The production of antibody molecules, by various means, is generally well understood. U.S. Pat. No. 6,331,415 (Cabilly et al.), for example, describes a method for the recombinant production of antibodies where the heavy and light chains are expressed simultaneously from a single vector or from two separate vectors in a single cell. Wibbenmeyer et al., (1999, Biochim Biophys Acta 1430(2):191-202) and Lee and Kwak (2003, J. Biotechnology 101:189-198) describe the production of monoclonal antibodies from separately produced heavy and light chains, using plasmids expressed in separate cultures of E. coli. Various other techniques relevant to the production of antibodies are provided in, e.g., Harlow, et al., ANTIBODIES: A LABORATORY MANUAL, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., (1988).

If desired, the antibody of the invention, e.g. any of the antibodies of FIG. 1 or FIG. 2, may be sequenced and the polynucleotide sequence may then be cloned into a vector for expression or propagation. The sequence encoding the antibody may be maintained in vector in a host cell and the host cell can then be expanded and frozen for future use. Production of recombinant monoclonal antibodies in cell culture can be carried out through cloning of antibody genes from B cells by means known in the art.

In another aspect, the invention provides an isolated nucleic acid comprising a sequence that codes for production of the recombinant antibody of the present invention.

An antibody encoding nucleic acid can have any suitable characteristics and comprise any suitable features or combinations thereof. Thus, for example, an antibody encoding nucleic acid may be in the form of DNA, RNA, or a hybrid thereof, and may include non-naturally-occurring bases, a modified backbone, e.g., a phosphorothioate backbone that promotes stability of the nucleic acid, or both. The nucleic acid advantageously may be incorporated in an expression cassette, vector or plasmid of the invention, comprising features that promote desired expression, replication, and/or selection in target host cell(s). Examples of such features include an origin of replication component, a selection gene component, a promoter component, an enhancer element component, a polyadenylation sequence component, a termination component, and the like, numerous suitable examples of which are known.

The present disclosure further provides the recombinant DNA constructs comprising one or more of the nucleotide sequences described herein. These recombinant constructs are used in connection with a vector, such as a plasmid, phagemid, phage or viral vector, into which a DNA molecule encoding any disclosed antibody is inserted.

Monoclonal antibodies are produced using any method that produces antibody molecules by continuous cell lines in culture. Examples of suitable methods for preparing monoclonal antibodies include the hybridoma methods of Kohler et al. (1975, Nature 256:495-497) and the human B-cell hybridoma method (Kozbor, 1984, J. Immunol. 133:3001; and Brodeur et al., 1987, Monoclonal Antibody Production Techniques and Applications, (Marcel Dekker, Inc., New York), pp. 51-63).

The invention moreover provides pharmaceutical compositions which comprise an antibody as described herein and a pharmaceutically acceptable carrier or excipient. These pharmaceutical compositions can be administered in accordance with the present invention as a bolus injection or infusion or by continuous infusion. Pharmaceutical carriers suitable for facilitating such means of administration are well known in the art.

Pharmaceutically acceptable carriers generally include any and all suitable solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like that are physiologically compatible with an antibody or related composition or combination provided by the invention. Further examples of pharmaceutically acceptable carriers include sterile water, saline, phosphate buffered saline, dextrose, glycerol, ethanol, and the like, as well as combinations of any thereof.

In one such aspect, an antibody can be combined with one or more carriers appropriate a desired route of administration, antibodies may be, e.g. admixed with any of lactose, sucrose, starch, cellulose esters of alkanoic acids, stearic acid, talc, magnesium stearate, magnesium oxide, sodium and calcium salts of phosphoric and sulphuric acids, acacia, gelatin, sodium alginate, polyvinylpyrrolidine, polyvinyl alcohol, and optionally further tableted or encapsulated for conventional administration. Alternatively, an antibody may be dissolved in saline, water, polyethylene glycol, propylene glycol, carboxymethyl cellulose colloidal solutions, ethanol, corn oil, peanut oil, cotton-seed oil, sesame oil, tragacanth gum, and/or various buffers. Other carriers, adjuvants, and modes of administration are well known in the pharmaceutical arts. A carrier may include a controlled release material or time delay material, such as glyceryl monostearate or glyceryl distearate alone or with a wax, or other materials well known in the art.

Additional pharmaceutically acceptable carriers are known in the art and described in, e.g. REMINGTON'S PHARMACEUTICAL SCIENCES. Liquid formulations can be solutions, emulsions or suspensions and can include excipients such as suspending agents, solubilizers, surfactants, preservatives, and chelating agents.

Pharmaceutical compositions are contemplated wherein an antibody of the present invention and one or more therapeutically active agents are formulated. Stable formulations of the antibody of the present invention are prepared for storage by mixing said immunoglobulin having the desired degree of purity with optional pharmaceutically acceptable carriers, excipients or stabilizers, in the form of lyophilized formulations or aqueous solutions. The formulations to be used for in vivo administration are specifically sterile, preferably in the form of a sterile aqueous solution. This is readily accomplished by filtration through sterile filtration membranes or other methods. The antibody and other therapeutically active agents disclosed herein may also be formulated as immunoliposomes, and/or entrapped in microcapsules.

Administration of the pharmaceutical composition comprising an antibody of the present invention, may be done in a variety of ways, including orally, subcutaneously, intravenously, intranasally, intraotically, transdermally, mucosal, topically, e.g., gels, salves, lotions, creams, etc., intraperitoneally, intramuscularly, intrapulmonary, e.g. employing inhalable technology or pulmonary delivery systems, vaginally, parenterally, rectally, or intraocularly.

Exemplary formulations as used for parenteral administration include those suitable for subcutaneous, intramuscular or intravenous injection as, for example, a sterile solution, emulsion or suspension.

In one embodiment, the antibody of the present invention is the only therapeutically active agent administered to a subject, e.g. as a disease modifying or preventing monotherapy.

In another embodiment, the antibody of the present invention is combined with further antibodies in a cocktail, e.g. combined in a mixture or kit of parts, to target E. coli, such that the cocktail contains more than one therapeutically active agents administered to a subject, e.g. as a disease modifying or preventing combination therapy.

Further, the antibody of the present invention may be administered in combination with one or more other therapeutic or prophylactic agents, including but not limited to standard treatment, e.g. antibiotics, steroid and non-steroid inhibitors of inflammation, and/or other antibody based therapy, e.g. employing anti-bacterial or anti-inflammatory agents.

A combination therapy is particularly employing a standard regimen, e.g. as used for treating MDR E. coli infection. This may include antibiotics, e.g. tygecycline, linezolide, methicillin and/or vancomycin.

In a combination therapy, the antibody may be administered as a mixture, or concomitantly with one or more other therapeutic regimens, e.g. either before, simultaneously or after concomitant therapy.

The biological properties of the antibody or the respective pharmaceutical preparations of the invention may be characterized ex vivo in cell, tissue, and whole organism experiments. As is known in the art, drugs are often tested in vivo in animals, including but not limited to mice, rats, rabbits, dogs, cats, pigs, and monkeys, in order to measure a drug's efficacy for treatment against a disease or disease model, or to measure a drug's pharmacokinetics, pharmacodynamics, toxicity, and other properties. The animals may be referred to as disease models. Therapeutics are often tested in mice, including but not limited to nude mice, SCID mice, xenograft mice, and transgenic mice (including knockins and knockouts). Such experimentation may provide meaningful data for determination of the potential of the antibody to be used as a therapeutic or as a prophylactic with the appropriate half-life, effector function, (cross-) neutralizing activity and/or immune response upon active or passive immunotherapy. Any organism, preferably mammals, may be used for testing. For example because of their genetic similarity to humans, primates, monkeys can be suitable therapeutic models, and thus may be used to test the efficacy, toxicity, pharmacokinetics, pharmacodynamics, half-life, or other property of the subject agent or composition. Tests in humans are ultimately required for approval as drugs, and thus of course these experiments are contemplated. Thus, the antibody and respective pharmaceutical compositions of the present invention may be tested in humans to determine their therapeutic or prophylactic efficacy, toxicity, immunogenicity, pharmacokinetics, and/or other clinical properties.

The invention also provides the subject antibody of the invention for diagnostic purposes, e.g. for use in methods of detecting and quantitatively determining the concentration of a bacterial load or antibody as immunoreagent or target in a biological fluid sample.

The invention also provides methods for detecting the degree of sepsis or MDR E. coli infection in a biological sample, e.g. the load of a sample with MDR E. co/i, such as a body fluid, comprising the step of contacting the sample with an antibody of the invention. The antibody of the invention may be employed in any known assay method, such as competitive binding assays, direct and indirect sandwich assays, Immunoprecipitation assays and enzyme-linked immunosorbent assays (ELISA).

The preferred diagnostic assay is performed as follows. Target antigen specific antibodies are immobilized on latex beads that are incubated with bacteria present in or isolated from body fluids. Positive reaction can be detected by naked eye due to the aggregation of the (possibly coloured) latex beads in the presence of the corresponding cognate antigen expressed on the surface of the bacteria.

A body fluid as used according to the present invention includes biological samples of a subject, such as tissue extract, urine, blood, serum, stool and phlegm.

In one embodiment the method comprises contacting a solid support with an excess of a certain type of antibody fragment which specifically forms a complex with the target, under conditions permitting the antibody to attach to the surface of the solid support. The resulting solid support to which the antibody is attached is then contacted with a biological fluid sample so that the target in the biological fluid binds to the antibody and forms a target-antibody complex. The complex can be labeled with a detectable marker. Alternatively, either the target or the antibody can be labeled before the formation the complex. For example, a detectable marker (label) can be conjugated to the antibody. The complex then can be detected and quantitatively determined thereby detecting and quantitatively determining the concentration of the target in the biological fluid sample.

For particular applications the antibody of the invention is conjugated to a label or reporter molecule, selected from the group consisting of organic molecules, enzyme labels, radioactive labels, colored labels, fluorescent labels, chromogenic labels, luminescent labels, haptens, digoxigenin, biotin, metal complexes, metals, colloidal gold and mixtures thereof. Antibodies conjugated to labels or reporter molecules may be used, for instance, in assay systems or diagnostic methods, e.g. to diagnose E. coli infection or disease conditions associated therewith.

The antibody of the invention may be conjugated to other molecules which allow the simple detection of said conjugate in, for instance, binding assays (e.g. ELISA) and binding studies.

Another aspect of the present invention provides a kit comprising an antibody, which may include, in addition to one or more antibodies, various diagnostic or therapeutic agents. A kit may also include instructions for use in a diagnostic or therapeutic method. Such instructions can be, for example, provided on a device included in the kit, e.g. tools or a device to prepare a biological sample for diagnostic purposes, such as separating a cell and/or protein containing fraction before determining the MDR E. coli load to diagnose a disease. Advantageously, such a kit includes an antibody and a diagnostic agent or reagent that can be used in one or more of the various diagnostic methods described herein. In another preferred embodiment, the kit includes an antibody, e.g. in the lyophilized form, optionally including instructions and a medium to reconstitute the lyophilizate, and/or in combination with pharmaceutically acceptable carrier(s) that can be mixed before use to form an injectable composition for near term administration.

The antibodies designated 8D5-1G10 and 8D10-C8, specifically any of the antibody light chains and/or heavy chains, is further characterized by the biological material deposited at the DSMZ—Deutsche Sammlung von Mikroorganismen und Zellkulturen, Mascheroder Weg 1b/Inhoffenstraβe 7B, 38124 Braunschweig (DE).

The deposits refer to transformed E. coli cultures, each containing a plasmid cloned with an insert of a gene of interest. The genes of interest are the variable domains of the heavy and light chains of the mouse monoclonal antibody 8D5-1G10 (IgG3), and the heavy and light chains of the mouse monoclonal antibody 8D10-C8 (IgG2b).

DSM 26763 is an E. coli host cell transformed with a plasmid comprising the variable domain coding sequence of the 8D5-1G10 light chain (8D5-1G10-LC). Escherichia coli 8D5-1G10-VL=DSM 26763, deposition date: Jan. 15, 2013; depositor: Arsanis Biosciences GmbH, Vienna, Austria.

DSM 26762 is an E. coli host cell transformed with a plasmid comprising the variable domain coding sequence of the 8D5-1G10 heavy chain (8D5-1G10-HC). Escherichia coli 8D5-1G10-VH=DSM 26762, deposition date: Jan. 15, 2013; depositor: Arsanis Biosciences GmbH, Vienna, Austria.

DSM 28171 is an E. coli host cell transformed with a plasmid comprising the variable domain coding sequence of the 8D10-C8 light chain (8D10-C8-LC). Escherichia coli 8D10-C8-VL=DSM 28171, deposition date: Dec. 11, 2013; depositor: Arsanis Biosciences GmbH, Vienna, Austria.

DSM 28172 is an E. coli host cell transformed with a plasmid comprising the variable domain coding sequence of the 8D10-C8 heavy chain (8D10-C8-HC). Escherichia coli 8D10-C8-VH=DSM 28172, deposition date: Dec. 11, 2013; depositor: Arsanis Biosciences GmbH, Vienna, Austria.

The subject matter of the following definitions is considered embodiments of the present invention:

1. An isolated antibody that specifically binds to O25b antigen of E. coli strains comprising at least an antibody heavy chain variable region (VH), which comprises any of the CDR1 to CDR3 sequences as listed in Table 1, which are designated according to the numbering system of Kabat, or as listed in Table 2, which are designated according to the IMGT numbering system, or functionally active CDR variants thereof.

2. The antibody of definition 1, which is

A)

selected from the group consisting of group members i) to xiv), wherein

i)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 1; and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 2; and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 3;

ii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 7; and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 8; and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 9;

iii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 11;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 12;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 13;

iv)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 17;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 18;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 19;

v)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 23;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 24;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 25;

vi)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 29;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 30;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 31;

vii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 34;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 35;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 36;

viii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 29;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 40;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 41;

ix)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 44;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 45;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 46;

x)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 50;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 51;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 52;

xi)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 50;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 55;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 56;

xii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 57;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 58;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 59;

xiii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 61;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 62;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 63;

xiv)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 66;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 67;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 68;

or

-   -   B) an antibody which is a functionally active variant of a         parent antibody that is any of the group members of A, which         comprises at least one functionally active CDR variant of any of         the CDR1, CDR2 or CDR3 of the parent antibody.

3. The antibody of definition 1 or 2, comprising

-   -   a) a VH amino acid sequence selected from any of the VH         sequences as depicted in FIG. 2, preferably of the antibody         heavy chain (HC) amino acid sequence which is any of SEQ ID 184         to SEQ ID 231 or any of SEQ ID 312 to SEQ ID 315;     -   b) an antibody heavy chain (HC) amino acid sequence which is any         of SEQ ID 184 to SEQ ID 231 or any of SEQ ID 312 to SEQ ID 315;         or     -   c) an antibody heavy chain (HC) amino acid sequence which is any         of SEQ ID 184 to SEQ ID 231 or any of SEQ ID 312 to SEQ ID 315,         and which is further comprising a deletion of the C-terminal         amino acid and/or a Q1E point mutation, if the first amino acid         of the VH sequence is a Q.

4. The antibody of any of definitions 1 to 3, which further comprises an antibody light chain variable region (VL), which comprises any of the CDR4 to CDR6 sequences as listed in Table 1, which are designated according to the numbering system of Kabat, or as listed in Table 2, which are designated according to the IMGT numbering system, or functionally active CDR variants thereof.

5. The antibody of definition 4, which is

A)

selected from the group consisting of group members i) to xiv), wherein

i)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 4; and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 5; and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 6;

ii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 10;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 5; and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 6;

iii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 14;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 15;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 16;

iv)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 20;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 21;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 22;

v)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 26;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 27;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 28;

vi)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 20;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 33;

vii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 37;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 27;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 38;

viii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 42;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 43;

ix)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 47;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 48;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 49;

x)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 53;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 54;

xi)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 57;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 54;

xii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 26;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 27;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 60;

xiii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 64;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 65;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 38;

xiv)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 69;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 70;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 71;

or

B) an antibody which is a functionally active variant of a parent antibody that is any of the group members of A, which comprises at least one functionally active CDR variant of any of the CDR4, CDR5 or CDR6 of the parent antibody.

6. The antibody of definition 4 or 5, comprising a VL amino acid sequence selected from any of the VL sequences as depicted in FIG. 2, preferably of an antibody light chain (LC) amino acid sequence which is any of SEQ ID 248 to SEQ ID 295 or any of SEQ ID 316 to SEQ ID 319, or comprising an antibody light chain (LC) amino acid sequence which is any of SEQ ID 248 to SEQ ID 295 or any of SEQ ID 316 to SEQ ID 319.

7. The antibody of definition 1, which is cross-specific to bind an epitope shared by the O25a and O25b antigens

8. The antibody of definition 7, which is

A)

selected from the group consisting of group members i) to vii), wherein

i)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 72;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 73;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 74;

ii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 77;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 78;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 79;

iii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 81;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 82;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 83;

iv)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 84;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 85;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 86;

v)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 77;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 89;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 90;

vi)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 92;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 93;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 94;

vii)

is an antibody which comprises

-   -   a) a CDR1 consisting of the amino acid sequence of SEQ ID 95;         and     -   b) a CDR2 consisting of the amino acid sequence of SEQ ID 96;         and     -   c) a CDR3 consisting of the amino acid sequence of SEQ ID 97;

or

B) an antibody which is a functionally active variant of a parent antibody that is any of the group members of A, which comprises at least one functionally active CDR variant of any of the CDR1, CDR2 or CDR3 of the parent antibody.

9. The antibody of definition 7 or 8, comprising

-   -   a) a VH amino acid sequence selected from any of the VH         sequences as depicted in FIG. 2, preferably of an antibody heavy         chain (HC) amino acid sequence which is any of SEQ ID 232 to SEQ         ID 247 or any of SEQ ID 312 to SEQ ID 315;     -   b) an antibody heavy chain (HC) amino acid sequence which is any         of SEQ ID 232 to SEQ ID 247 or any of SEQ ID 312 to SEQ ID 315;         or     -   c) an antibody heavy chain (HC) amino acid sequence which is any         of SEQ ID 232 to SEQ ID 247 or any of SEQ ID 312 to SEQ ID 315,         and which is further comprising a deletion of the C-terminal         amino acid and/or a Q1E point mutation, if the first amino acid         of the VH sequence is a Q.

10. The antibody of any of definitions 7 to 9, which further comprises an antibody light chain variable region (VL), which comprises any of the CDR4 to CDR6 sequences as listed in Table 1, which are designated according to the numbering system of Kabat, or as listed in Table 2, which are designated according to the IMGT numbering system, or functionally active CDR variants thereof.

11. The antibody of definition 10, which is

A)

selected from the group consisting of group members i) to vi), wherein

i)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 75;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 76;

ii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 75;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 80;

iii)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 69;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 70;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 71;

iv)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 42;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 87;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 88;

v)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 37;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 27;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 91;

vi)

is an antibody which comprises

-   -   a) a CDR4 consisting of the amino acid sequence of SEQ ID 42;         and     -   b) a CDR5 consisting of the amino acid sequence of SEQ ID 32;         and     -   c) a CDR6 consisting of the amino acid sequence of SEQ ID 88;

or

B) an antibody which is a functionally active variant of a parent antibody that is any of the group members of A, which comprises at least one functionally active CDR variant of any of the CDR4, CDR5 or CDR6 of the parent antibody.

12. The antibody of definitions 10 or 11, comprising a VL amino acid sequence selected from any of the VL sequences as depicted in FIG. 2, preferably of an antibody light chain (LC) amino acid sequence which is any of SEQ ID 296 to SEQ ID 311 or any of SEQ ID 316 to SEQ ID 319, or comprising an antibody light chain (LC) amino acid sequence which is any of SEQ ID 296 to SEQ ID 311 or any of SEQ ID 316 to SEQ ID 319.

13. The antibody of any of definitions 1 to 12, which comprises

-   -   a) the CDR1-CDR6 sequences of any of the antibodies as listed in         Table 1; or     -   b) the VH and VL sequences of any of the antibodies as depicted         in FIG. 2; or     -   c) the HC and LC sequences of any of the antibodies as listed in         FIG. 2; or     -   d) which is a functionally active variant of a parent antibody         that is characterized by the sequences of a)-c),     -   preferably wherein         -   i. the functionally active variant comprises at least one             functionally active CDR variant of any of the CDR1-CDR6 of             the parent antibody; and/or         -   ii. the functionally active variant comprises at least one             point mutation in the framework region of any of the VH and             VL sequences and/or the HC and LC sequences of the parent             antibody, optionally comprising a Q1E point mutation, if the             first amino acid of the VH framework region (VH FR1) is a Q;     -   and further wherein         -   iii. the functionally active variant has a specificity to             bind the same epitope as the parent antibody; and/or         -   iv. the functionally active variant is a human, humanized,             chimeric or murine and/or affinity matured variant of the             parent antibody.

14. The antibody of definition 13, which is a functionally active derivative of the antibody designated 8D5-1G10 or 8D10-C8, which comprises at least one point mutation in any of the CDR1-CDR6, preferably wherein the antibody has a specificity to bind the same epitope as the antibody designated as 8D5-1G10 and 8D10-C8, respectively.

15. The antibody of any of definitions 1 to 14, comprising a functionally active CDR variant of any of the CDR sequences as listed in Table 1, wherein the functionally active CDR variant comprises at least one of

a) 1, 2, or 3 point mutations in the parent CDR sequence; and/or

b) 1 or 2 point mutations in any of the four C-terminal or four N-terminal, or four centric amino acid positions of the parent CDR sequence; and/or

c) at least 60% sequence identity with the parent CDR sequence.

16. The antibody of definition 15, wherein the functionally active CDR variant comprises 1 or 2 point mutations in any CDR sequence consisting of less than 4 or 5 amino acids.

17. The antibody of any of definitions 1 to 16, which comprises CDR and framework sequences, wherein at least one of the CDR and framework sequences includes human, humanized, chimeric, murine or affinity matured sequences, preferably wherein the framework sequences are of an IgG antibody.

18. The antibody of any of definitions 1 to 17, which has an affinity to bind the O25b antigen with a Kd of less than 10⁻⁶M, preferably less than 10⁻⁷M or less than 10⁻⁸M.

19. The antibody of any of definitions 1 to 18, which preferentially binds to the O25b antigen relative to the O25a antigen of E. coli, or at least with equal affinity towards both antigens.

20. The antibody of any of definitions 1 to 19, which is a full-length monoclonal antibody, an antibody fragment thereof comprising at least one antibody domain incorporating the antigen binding site, or a fusion protein comprising at least one antibody domain incorporating the antigen binding site.

21. The antibody of any of definitions 1 to 19, for use in treating a subject at risk of or suffering from an E. coli infection comprising administering to the subject an effective amount of the antibody to limit the infection in the subject or to ameliorate a disease condition resulting from said infection, preferably for treatment or prophylaxis of pyelonephritis, secondary bacteremia, sepsis, peritonitis, meningitis, and ventilator-associated pneumonia.

22. A pharmaceutical preparation comprising the antibody of any of definitions 1 to 20, preferably comprising a parenteral or mucosal formulation, optionally containing a pharmaceutically acceptable carrier or excipient.

23. The antibody of any of definitions 1 to 20, for diagnostic use to determine E. coli infection or bacteremia in a subject caused by an E. coli strain, such as upper and lower urinary tract infections, including cystitis or urethritis, ascending or hematogenous pyelonephritis, especially in diabetic patients, as well as with bacteremia, sepsis, peritonitis, or intestinal colonization.

24. Diagnostic preparation of the antibody of any of definitions 1 to 20, comprising the antibody and a further diagnostic reagent in a composition or a kit of parts, comprising the components

-   -   a) the antibody; and     -   b) the further diagnostic reagent;     -   c) and optionally a solid phase to immobilize at least one of         the antibody and the diagnostic reagent.

25. Method of diagnosing E. coli infection or bacteremia in a subject caused by an E. coli strain, comprising

-   -   a) providing an antibody according to any of definitions 1 to         20, and     -   b) detecting if the antibody specifically immunoreacts with the         O25b antigen in a biological sample of the subject to be tested,         preferably by an agglutination test, thereby diagnosing MDR E.         coli infection or bacteremia.

26. Isolated nucleic acid encoding an antibody of any of the definitions 1 to 20.

27. An expression cassette or a plasmid comprising a coding sequence to express

-   -   a) a VH and/or VL of an antibody of any of definitions 1 to 20;         or     -   b) or a HC and/or LC of an antibody of any of definitions 1 to         20.

28. A host cell comprising an expression cassette or a plasmid of definition 27.

29. Method of producing an antibody according to any of definitions 1 to 20, wherein a host cell according to definition 28 is cultivated or maintained under conditions to produce said antibody.

The foregoing description will be more fully understood with reference to the following examples. Such examples are, however, merely representative of methods of practicing one or more embodiments of the present invention and should not be read as limiting the scope of invention.

EXAMPLES Example 1: Generation of O25b-Specific Antibodies

A non-encapsulated mutant of the representative ST131-O25b:H4 strain 81009 (81009Δkps::kan, [Szijarto et al, FEMS Microbiol Lett, 2012]) was generated by replacing the kps cluster (encoding capsular synthesis) with a cassette encoding kanamycin resistance. Sublethal doses of live or formaldehyde-inactivated cells of this mutant as well as sublethal doses of the parental wild-type strain were used to immunize mice 4 times at two-week intervals. Subsequently, serum samples obtained from the mice were analysed, and the spleen of the mouse showing the highest IgG titer against O25b antigen (in ELISA, immunoblotting, and surface staining) was used for hybridoma generation. Following sub-cloning, several hybridoma clones were selected, which secreted antibodies specific to purified O25b antigens as well as bound to the surface of live wild-type E. coli strains expressing O25b antigens. The mouse antibodies generated covered all possible murine isotypes, i.e. IgG1, IgG2a, IgG2b, and IgG3. The variable domains of the heavy (VH) and light (VL) chains of O25b-specific mAbs were amplified from hybridoma clones by using RT-PCR with degenerated heavy and light chain primers and sequenced. Sequences were analysed with BLAST for Ig database as well as with IMGT/V-QUEST, and CDR regions were defined according to Kabat nomenclature (FIG. 1, Table 1).

Selected hybridoma clones were expressed as chimeric mAbs, (i.e. the mouse variable regions were fused to human IgG1 constant domains as well as to kappa light chains). Moreover, humanized mAbs were generated by grafting hypervariable (CDR) mouse sequences into human framework sequences that had in silico been predicted the most compatible to the original mouse frameworks. The chimeric and humanized mAbs were expressed by mammalian cells, purified through protein A columns and used in assays shown in the subsequent examples (see below).

Example 2: Binding Characteristics

The specificity of chimeric and humanized mAbs was confirmed by immunoblot analysis using purified LPS (FIG. 3). All mAbs recognized the LPS molecules from ST131 strains containing the O25b antigen, however were different in their cross-reactive potential to O25a LPS antigens. While some mAbs reacted exclusively to O25b antigen, others (from lineage 4D5—FIG. 4 ii; middle panel) were cross-reactive to O25a. None of the mAbs reacted to LPS molecules carrying unrelated O-antigen (e.g. O55). Antibody binding characteristics were further investigated by biolayer inferometry (BLI). Binding of the O25b mAbs (chimeric and humanized) to biotinylated O25b polysaccharide was performed by immobilizing the biotinylated antigen on streptavidin sensors (ForteBio, Pall Life Sciences) and monitoring the association of the mAbs (8-10 μg/mL) to the preloaded sensors for 10 min in PBS containing 1% BSA, followed by dissociation (5 minutes) in the same buffer. The K_(d), k_(on) and k_(off) values were determined using the Data Analysis 7 software (ForteBio, Pall Life Sciences). All mAbs investigated showed an avid binding affinity between 9.5-211 nM in this setup (FIG. 4).

Binding of the mAbs to the native antigen on the bacterial surface was tested by flow cytometry. All antibodies bound to several different clinical isolates determined to be ST131-O25b:H4 strains. With respect to binding to strains expressing the O25a antigen there were two types of mAbs identified. One group did not bind to the surface of O25a strains, while the other group of mAbs was cross-reactive to strains expressing the related O25a strains. None of the mAbs, however, could bind to any E. coli strains expressing unrelated antigens O-types (FIG. 5i ). There was a good correlation between cross-reactivity exhibited by flow cytometric measurements (FIG. 5i ) and immunoblotting (FIG. 3).

In order to investigate surface binding in more details, ST131 strain 30 (Novais A. et al, Antimicrob Agents Chemother 2012 56(5):2763-6) was cultured either in LB (i.e. common laboratory growth medium) or inactivated human serum (in order to mimic in vivo-like growth conditions) until mid-logarithmic phase of growth and following washing was stained with the purified O25b-reactive mAbs at a dilution range of 0.025-40 μg/ml. Following washing an Alexa 488 labelled anti-human IgG was applied at a concentration of 4 μg/mL and the fluorescent intensity was measured by flow cytometry (BD Accuri C6 Flow Cytometer). A representative experiment shown on FIG. 5 ii) A confirmed that all mAbs tested were able to bind to the surface of the investigated strain at a dose dependent manner. The binding intensity was somewhat reduced upon growing bacteria in serum (vs. LB), however, remained highly significant for all mAbs tested (FIG. 5 ii) B). In order to prove that surface binding is irrespective of the genetic differences within ST131-O25b strains, a well-characterized panel of ST131 strains comprising different pulsotypes was investigated (Peirano et al, Antimicrob. Agents Chemother. 2014, 58(7):3762). Data summarized in FIG. 5 ii) C proved that all three mAbs investigated stained strongly the surface of all representative strains except that for pulsotype ‘O’, which had in fact been reported to belong to the ST131:O16 lineage. Flow cytometry experiments, therefore, could prove broad binding spectrum throughout the ST131:O25b lineage and this binding was retained when bacteria had been grown in human serum (i.e. under in vivo-like conditions).

Example 3: Antibacterial Effect of O25b Specific mAbs

The potential protective effect of selected O25b-specific chimeric mAbs and humanized mAbs (with or without cross-reactivity to O25a) was tested in a lethal murine bacteremia model. Groups of 5 mice received 100 μg of purified mAbs in PBS, intraperitoneally. 24 h later mice were challenged intravenously by a lethal dose (previously determined in a pilot experiment) of E. coli strain ST131 81009 ([Szijarto et al, (FEMS Microbiol Lett 2012; 332:131-6)) expressing the O25b antigen. 24 h later mice were challenged intravenously by a lethal dose (10⁸ CFU as previously determined in a pilot experiment) of E. coli ST131 strain 81009 (Szijarto et al. FEMS Microbiol Lett 2012; 332:131-6) proven to express the O25b antigen. Lethality of mice was monitored daily. FIG. 6i ) shows that while 100% of the mice immunized with 100 μg of a control mAb with irrelevant specificity succumbed to infection, all O25b specific mAbs tested provided statistically (Logrank test) significant increase in survival over the 14 days post-infection period monitored.

In order to corroborate this in vivo data, bactericidal effect of purified mAbs was also tested in vitro. Bacteria were cultured to mid-log phase of growth in Luria Bertani (LB) broth or heat inactivated normal human serum. 2 ml of bacterial cultures were washed twice in PBS. Serum bactericidal assay (SBA) was performed in 50% depleted human serum pool diluted with DPBS supplemented with calcium and magnesium. Reaction mixture contained ˜5×10³ CFU from LB- or serum grown mid-log phase bacterial suspension and 2.5 or 10 μg/ml mAb, respectively. Mixtures without any antibody and with isotype matched irrelevant mAb were included as controls. Bacteria were enumerated by plating appropriate dilutions following 3 h (in case of LB-grown bacteria) or 5 h (in case of serum-grown bacteria) incubation at 37° C. with shaking at 410 RPM. Killing mediated by specific mAbs was expressed as percent relative to incoculum (starting CFU) (FIG. 7i ) or as

$\begin{matrix} {{{killing}{\mspace{11mu} \;}(\%)} = {100 - {\left( {\frac{{CFU}\; ({mAb})}{{CFU}\; \left( {{without}\mspace{14mu} {antibody}} \right)}*100} \right).}}} & \left( {{{Fig}.\mspace{14mu} 7}{ii}} \right) \end{matrix}$

As depicted on FIG. 7i ), all mAbs tested were able to significantly decrease the CFU over the 3 hours study period. In contrast, the bacteria mixed with an irrelevant mAb or no antibodies showed growth in this medium. In case complement was inactivated in the serum samples (by 30 min. incubation at 56° C.), no bacterial killing was observed by any mAbs (data not shown). These results prove that O25b-specific mAb-s (with or without cross-reactivity to O25a) can trigger complement mediated bactericidal effect.

Additional experiments confirmed this activity (FIG. 7 ii). While an isotype-matched irrelevant mAb could not elicit bactericidal activity, all anti-O25b mAbs were able to significantly decrease the CFU over the 3 hours study period against both ST131-O25b strains tested (FIGS. 7 iiA, B and D). No bacterial killing was observed by any mAbs in case complement was heat inactivated in the serum samples (by 30 min incubation at 56° C., data not shown). These results prove that O25b-specific mAb-s (with or without cross-reactivity to O25a) can trigger complement mediated bactericidal effect. In order to confirm that this mode of action may be relevant in the in vivo protection observed (see above) we performed the same assay using bacteria grown in human serum (in contrast to bacterial culture medium, i.e. LB). The importance of growing bacteria under “in vivo-like” conditions is that the surface of bacteria and hence accessibility of antigens may be highly different when grown at different conditions due to expressional realignment of surface bacterial components (Miajlovic H et al., Infect. Immun. 82:298-305, 2014.) As depicted on FIG. 7 iiC, O25b-specific humanized mAbs were able to elicit significant bacterial killing even following pre-conditioning (i.e. growing) bacteria in human serum. For the maximal bactericidal effect, however, a higher mAb dose (10 μg/ml) as well as a longer incubation period (5 h) was required.

Example 4. Endotoxin Neutralizing Potential of O25b Specific mAbs

Since LPS has endotoxic potential, we considered important to test potential neutralizing capacity of mAbs binding to the O25b antigen within the LPS molecules.

Mice are inheritedly more resistant to endotoxin than humans, however, they can be made susceptible to minute amounts of purified LPS by the administration of the hepatotoxic carbohydrate D-GalN (Galanos C et al., Proc. Natl. Acad. Sci. U.S.A. 76:5939-5943, 1979). Mice were immunized with 100 or 25 μg of mAbs prophylactically 24 h prior to a simultaneously applied i.p. sensitization with 20 mg/mouse D-GalN and i.v. challenge with a lethal dose (1 ng) of purified O25b LPS. FIG. 8 shows representative experiments for humanized mAbs showing significant and dose dependent protection against lethal endotoxaemia.

In order to elucidate more on this mode of action, humanized O25b specific mAbs were investigated in an in vitro neutralization assays. LPS signals through the toll like receptor-4 (TLR-4)/MD2 receptor complex, which is responsible for eliciting septic shock in vivo. To assess neutralization of LPS signalling through the TLR-4 complex, we used the commercial HEK-Blue system (InvivoGen). This assay utilizes HEK cells transformed to express the human TLR-4 complex. Signalling through this receptor induces secretion of an enzyme, that is quantified through a chromogenic substrate. FIG. 9A shows that purified O25b LPS has a dose dependent activity in this assay. Neutralizing mAbs are able to inhibit at a dose dependent manner the signal elicited by a standard concentration of endotoxin (FIG. 9B). The IC50 values (concentration of mAbs neutralizing 50% of the maximal effect) make it possible to compare the neutralizing potential of various mAbs. FIG. 9C summarizes the neutralizing efficacy of representative humanized O25b-reactive mAbs. 

1. An isolated antibody that specifically binds to O25b antigen of E. coli strains comprising at least an antibody heavy chain variable region (VH), which comprises any of the CDR1 to CDR3 sequences as listed in Table 1, which are designated according to the numbering system of Kabat, or as listed in Table 2, which are designated according to the IMGT numbering system, or functionally active CDR variants thereof.
 2. The antibody of claim 1, which is A) selected from the group consisting of group members i) to xiv), wherein i) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 1; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 2; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 3; ii) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 7; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 8; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 9; iii) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 11; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 12; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 13; iv) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 17; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 18; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 19; v) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 23; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 24; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 25; vi) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 29; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 30; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 31; vii) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 34; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 35; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 36; viii) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 29; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 40; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 41; ix) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 44; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 45; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 46; x) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 50; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 51; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 52; xi) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 50; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 55; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 56; xii) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 57; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 58; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 59; xiii) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 61; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 62; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 63; xiv) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 66; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 67; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 68; or B) an antibody which is a functionally active variant of a parent antibody that is any of the group members of A, which comprises at least one functionally active CDR variant of any of the CDR1, CDR2 or CDR3 of the parent antibody.
 3. The antibody of claim 1, comprising a) a VH amino acid sequence selected from any of the VH sequences as depicted in FIG. 2; b) an antibody heavy chain (HC) amino acid sequence which is any of SEQ ID 184 to SEQ ID 231 or any of SEQ ID 312 to SEQ ID 315; or c) an antibody heavy chain (HC) amino acid sequence which is any of SEQ ID 184 to SEQ ID 231 or any of SEQ ID 312 to SEQ ID 315, and which is further comprising a deletion of the C-terminal amino acid and/or a Q1E point mutation, if the first amino acid of the VH sequence is a Q.
 4. The antibody of claim 3, which further comprises an antibody light chain variable region (VL), which comprises any of the CDR4 to CDR6 sequences as listed in Table 1, which are designated according to the numbering system of Kabat, or as listed in Table 2, which are designated according to the IMGT numbering system, or functionally active CDR variants thereof.
 5. The antibody of claim 4, which is A) selected from the group consisting of group members i) to xiv), wherein i) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 4; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 5; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 6; ii) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 10; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 5; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 6; iii) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 14; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 15; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 16; iv) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 20; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 21; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 22; v) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 26; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 27; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 28; vi) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 20; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 32; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 33; vii) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 37; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 27; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 38; viii) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 42; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 32; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 43; ix) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 47; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 48; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 49; x) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 53; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 32; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 54; xi) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 57; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 32; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 54; xii) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 26; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 27; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 60; xiii) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 64; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 65; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 38; xiv) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 69; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 70; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 71; or B) an antibody which is a functionally active variant of a parent antibody that is any of the group members of A, which comprises at least one functionally active CDR variant of any of the CDR4, CDR5 or CDR6 of the parent antibody.
 6. The antibody of claim 4, comprising a VL amino acid sequence selected from any of the VL sequences as depicted in FIG.
 2. 7. The antibody of claim 1, which is cross-specific to bind an epitope shared by the O25a and O25b antigens, specifically which antibody preferentially binds to the O25b antigen relative to the O25a antigen of E. coli, or at least with equal affinity towards both antigens.
 8. The antibody of claim 7, which is A) selected from the group consisting of group members i) to vii), wherein i) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 72; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 73; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 74; ii) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 77; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 78; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 79; iii) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 81; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 82; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 83; iv) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 84; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 85; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 86; v) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 77; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 89; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 90; vi) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 92; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 93; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 94; vii) is an antibody which comprises a) a CDR1 consisting of the amino acid sequence of SEQ ID 95; and b) a CDR2 consisting of the amino acid sequence of SEQ ID 96; and c) a CDR3 consisting of the amino acid sequence of SEQ ID 97; or B) an antibody which is a functionally active variant of a parent antibody that is any of the group members of A, which comprises at least one functionally active CDR variant of any of the CDR1, CDR2 or CDR3 of the parent antibody.
 9. The antibody of claim 7, comprising a) a VH amino acid sequence selected from any of the VH sequences as depicted in FIG. 2; b) an antibody heavy chain (HC) amino acid sequence which is any of SEQ ID 232 to SEQ ID 247 or any of SEQ ID 312 to SEQ ID 315; or c) an antibody heavy chain (HC) amino acid sequence which is any of SEQ ID 232 to SEQ ID 247 or any of SEQ ID 312 to SEQ ID 315, and which is further comprising a deletion of the C-terminal amino acid and/or a Q1E point mutation, if the first amino acid of the VH sequence is a Q.
 10. The antibody of claim 7, which further comprises an antibody light chain variable region (VL), which comprises any of the CDR4 to CDR6 sequences as listed in Table 1, which are designated according to the numbering system of Kabat, or as listed in Table 2, which are designated according to the IMGT numbering system, or functionally active CDR variants thereof.
 11. The antibody of claim 10, which is A) selected from the group consisting of group members i) to vi), wherein i) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 75; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 32; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 76; ii) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 75; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 32; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 80; iii) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 69; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 70; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 71; iv) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 42; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 87; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 88; v) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 37; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 27; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 91; vi) is an antibody which comprises a) a CDR4 consisting of the amino acid sequence of SEQ ID 42; and b) a CDR5 consisting of the amino acid sequence of SEQ ID 32; and c) a CDR6 consisting of the amino acid sequence of SEQ ID 88; or B) an antibody which is a functionally active variant of a parent antibody that is any of the group members of A, which comprises at least one functionally active CDR variant of any of the CDR4, CDR5 or CDR6 of the parent antibody.
 12. The antibody of claim 10, comprising a VL amino acid sequence selected from any of the VL sequences as depicted in FIG.
 2. 13. The antibody of claim 1, which comprises a) the CDR1-CDR6 sequences of any of the antibodies as listed in Table 1; or b) the VH and VL sequences of any of the antibodies as depicted in FIG. 2; or c) the HC and LC sequences of any of the antibodies as listed in FIG. 2; or which is a functionally active variant of a parent antibody that is characterized by the sequences of a)-c); ii.; and further wherein iii. the functionally active variant has a specificity to bind the same epitope as the parent antibody; and/or iv. the functionally active variant is a human, humanized, chimeric or murine and/or affinity matured variant of the parent antibody.
 14. The antibody of claim 1, comprising a functionally active CDR variant of any of the CDR sequences as listed in Table 1, wherein the functionally active CDR variant comprises at least one of a) 1, 2, or 3 point mutations in the parent CDR sequence; and/or b) 1 or 2 point mutations in any of the four C-terminal or four N-terminal, or four centric amino acid positions of the parent CDR sequence; and/or c) at least 60% sequence identity with the parent CDR sequence.
 15. The antibody of claim 1, which comprises CDR and framework sequences, wherein at least one of the CDR and framework sequences includes human, humanized, chimeric, murine or affinity matured sequences.
 16. The antibody of any of claims 1 to 15 claim 1, which has an affinity to bind the O25b antigen with a Kd of less than 10⁻⁶M.
 17. The antibody of claim 1, for use in treating a subject at risk of or suffering from an E. coli infection comprising administering to the subject an effective amount of the antibody to limit the infection in the subject or to ameliorate a disease condition resulting from said infection.
 18. A pharmaceutical preparation, comprising the antibody of any of claims 1 to 16 claim 1 in a pharmaceutically acceptable carrier or excipient.
 19. (canceled)
 20. A kit comprising the components a) the antibody of claim 1; b) a further diagnostic reagent; c) and a solid phase to immobilize at least one of the antibody and the diagnostic reagent.
 21. A method of diagnosing E. coli infection or bacteremia in a subject caused by an E. coli strain, comprising a) providing an antibody according to claim 1, and b) detecting if the antibody specifically immunoreacts with the O25b antigen in a biological sample of the subject to be tested, thereby diagnosing MDR E. coli infection or bacteremia.
 22. An isolated nucleic acid encoding an antibody of claim
 1. 23. An expression cassette or a plasmid comprising a coding sequence to express a) a VH and/or VL of an antibody of claim 1; or b) or a HC and/or LC of an antibody of claim
 1. 24. A host cell comprising an expression cassette or a plasmid of claim
 23. 25. A method of producing an antibody, wherein a host cell according to claim 24 is cultivated or maintained under conditions to produce said antibody.
 26. The antibody of claim 3, wherein the VH amino acid sequence is of an antibody heavy chain (HC) amino acid sequence which is any of SEQ ID 184 to SEQ ID 231 or any of SEQ ID 312 to SEQ ID
 315. 27. The antibody of claim 6, wherein the VL amino acid sequence of is of an antibody light chain (LC) amino acid sequence which is any of SEQ ID 248 to SEQ ID 295 or any of SEQ ID 316 to SEQ ID 319, or comprising an antibody light chain (LC) amino acid sequence which is any of SEQ ID 248 to SEQ ID 295 or any of SEQ ID 316 to SEQ ID
 319. 28. The antibody of claim 9, wherein the VH amino acid sequence is of an antibody heavy chain (HC) amino acid sequence which is any of SEQ ID 232 to SEQ ID 247 or any of SEQ ID 312 to SEQ ID
 315. 29. The antibody of claim 12, wherein the VL amino acid sequence of is of an antibody light chain (LC) amino acid sequence which is any of SEQ ID 296 to SEQ ID 311 or any of SEQ ID 316 to SEQ ID 319, or comprising an antibody light chain (LC) amino acid sequence which is any of SEQ ID 296 to SEQ ID 311 or any of SEQ ID 316 to SEQ ID
 319. 30. The antibody of claim 13, wherein i. the functionally active variant comprises at least one functionally active CDR variant of any of the CDR1-CDR6 of the parent antibody; and/or ii. the functionally active variant comprises at least one point mutation in the framework region of any of the VH and VL sequences and/or the HC and LC sequences of the parent antibody, optionally comprising a Q1E point mutation, if the first amino acid of the VH framework region (VH FR1) is a Q.
 31. The antibody of claim 14, wherein the functionally active CDR variant comprises 1 or 2 point mutations in any CDR sequence consisting of less than 4 or 5 amino acids. 